The engine guts I described are pretty much what I have been running for 11 years and 85k miles in a MOST roadable engine. The Bonneville head is the biggest difference, and I specified the MAP pistons, because the Morgo AE pistons I am running in my Routt kit are harder to get, at .060 over.
I'd use the early unit frames because of the 3 degrees less rake, shortening the wheelbase and quickening the steering....also moves the center of mass slightly forward. I would use the 69-on swingarm (or T150), as they are stiffer. I selected the late rear frame because I like the easily removable sidecover which doesn't crack and the early frames used a solid mounted oil tank, and I prefer the rubber mounts on that.
The cams I use have more overlap than the stock ones, lowering the effective pressure in the cylinder at low rpm, thereby reducing the tendency to ping when accelerating from lower rpm even though the bike runs the higher compression pistons, and the five speed is effectively a closer ratio four speed with an overdrive when used with the high final drive ratio, allowing you to keep the engine revs high enough to minimize pinging without overrevving or getting buzzy. Keeping the mixture a tad on the rich side, enough to grey the plug electrodes, but not enough to foul the plugs, also keeps the bike tractable, and heat is a concern here in Hawaii.
I didn't go into detail about the modified oil system. The pressure relief valve won't be in the case anymore. The stock setup dumps excess oil into the timing cover and then back to the tank. This provides most of the lubricating oil for the timing pinions. It also provides drag and doesn't do anything to cool the hottest part of the engine, the head or cylinders......Sooooo I plan to fit a Morgo gear oil pump and then to make an oil manifold. The oil pressure relief valve would be mounted in the end of the manifold and high pressure oil would be fed from the plug that replaces the valve in the case to the manifold via Earls ss/teflon hose. This hose will not pass oil until the pressure in the main oil gallery of the engine raises to the 85 pounds for the engine, then, as the stock bike does, it begins to leak off enough oil to keep the pressure at that level. The oil that bypasses the valve goes into the maifold which feeds the machined Barnett valve adjusting caps. In the end of each banjo bolt, on the inside of the cap, is a Mikuni main jet. This allows me to easily adjust the flow of oil to the valves....more on the exhaust, less on the inlet. The drains in the tappet blocks are drilled larger to allow the additional oil to drain back to the sump, also providing more oil for the tappets and cam faces. The larger drain holes also allow for better breathing from the rocker boxes, reducing leaks.....theoretically. There is another pressure relief valve in the other end of the manifold and when the pressure reaches 95 psi in the manifold, it begins to bleed off oil to a line that feeds back to the timing cover, to lube the timing gears and dispose of the excess oil in the system. On the way back to the tank, the oil passes through a filter/cooler. A similar system works pretty well for my Thruxton, except they use two oil pumps. I thought about that, too. Originally, I was going to fit a second oil pump to the end of the exhaust camshaft, replacing the tach drive, which I don't use. The first iteration of this was to make a system for the gearbox lube, to keep it cool and filter metal bits out. But I think that is probably gilding the lily. A few of the strong little Neodymium/Iron/Boron magnets in strategic locations would likely do as well. I had a couple of them stuck on the back of the oil tank which are now stuck to various bits of the Thruxton oil system, including the filter can. They won't pick up little bits of nonferrous metals, but I suspect they are less of a danger than the hard steel bits.
Now, if we are talking stock forks, certainly the late shuttle valve steel forks would be my first choice, along with a lightened Iron hub DLS Triumph/BSA brake. The only other choice would be the disc brake setup. I think I could bore out the lower legs and the yokes enough to fit 35mm Ceriani stanchions and guts, or perhaps Betor. Then get either the Lockheed calipers or go large and get some four pot billet items, drill the discs, fit a 13mm bore master from those French guys or go cheap with the Grimeca. If we can switch discs, then the 12" floater would go on the list. A fork brace would be a good idea for a single disc setup. EBC brake pads. Earl-s -2 hose.
The target is a 350 lb. reliable roadster.....kinda like my 68, but with more Bonneville power. I've been running a TR head with 32mm Concentric, and have been ok with the power delivery vs simplicity. I would like to try out a single 34 or 36mm Dellorto pumper carb and do a dyno and riding comparison. Well, I DO have an extra TR6 head.........
OH....If they become available again....I'd get one of the Aerco ten bolt 750 cylinders for long rod engines and fit the 10 bolt Bonneville or TR head. Nag Bill Getty at JRC Engineering to get them made again.
Oh, and some years ago, I had a set of Carrillo-style beam rods in ALLOY with steel caps and replaceable bronze bushes. I don't know who made them, but they were just GREAT. Maybe I could nag Carrillo to make them now, with a little help.