A bit of progress:

Does the rear arm clear the engine? Nice job so far

The suspension bottoms-out just before the upper arm hits the pullstarter. If I can make an adapter plate to attach the Traxxas EZ-Start, that will give me a few more precious millimeters to work with. I may also be able to use a front-left upper arm on the rear, which would give me even more room to work with.

Also, I discovered the HPI T3.0 spiral carb will fit this engine without modifications, and it has a nearly-identical throat diameter too. So there's my solution for fitting a 2-needle carb to this engine for better tuning.

I wish I could make solid engine mounts rather than using standoff posts, but I would need a drill press to make my own engine mounts, and I don't have the space for a tool that bulky.

The posts should be fine. But, the chassis will flex, chewing up your spur gear unless you triangulate the setup somehow. Maybe another piece of metal from the "passenger side" engine mounting lug, to somewhere else on the chassis. The Revos are known for flex on that section of the chassis even WITH the stock mount which is braced from underneath.

CNC mostly. Ive done progamming and some cad.

Good to know, but it's worth noting that unlike the stock motor mount, my flat-plate adapter anchors both of the support brackets together with four screws. The stock motor mount only has one screw and one pivot-pin, and that one screw just pinches the pivoting motor mount between the two support brackets, rather than bolting solidly to each of the support brackets in multiple places. At this point I'm not too worried about flex...though I will let reality prove me wrong if it will.

Well, are you seriously able to make parts? A couple others have come before with access to the equipment but nothing ever really came of it.
Looking forward to seeing that beast run! Got any kind of ETA on that?

An overhead cam design driven by a belt would be the easiest to design as well as the best for high rpm operation. Less mass in the valvetrain.
So far, my O.S. Fs62-v is maxxing out around 20,000 rpm, and I'm sure it's just reached some fundamental limit because it will not go further.

I agree that an OHC or DOHC design would be best, it might create some additional problems on some parts but also make other things possible.
A pent roof design with either buckets or followers should work, that might give the possibility to run 2 intake valves, with the glow plug positioned well and have good squish pads.
The big problem is getting the cam(s) good, that is super critical for rpm. The other thing needed to make power at high rpm (and not just over rev it) is getting the intake and exhaust right, and that will probably be a problem to fit under most bodies.
But problems are made to be solved!

I’ve followed this thread on and off for awhile and have considered doing a 4-stroke build myself. I have a line on an LST XXL2 chassis that is build around a 4-stroke engine. I have an Enya .46 and an Enya .60 at my disposal - with the .46 probably being the one I use due to its smaller size and similar power to the .60. I think the LST driveline is more than strong enough to handle the power, but starting the engine will likely be my biggest issue since there is no possibility of using an electric or pull starter on it. I don’t even think I could make my bump box work unless the flywheel is huge.

thats what i plan on doing just cause its easier to design and produce. The biggest obstacle is designing a head thatll fit everything and allow for good design practice.

The biggest bumps in power Ive found are from a free flowing exhaust. My most power yet is from a 2 stroke pipe actually. Also way quieter. Ive got a car cam from speedworks, havent tried it just yet.
Well, a huge flywheel is a necessity anyways if you dont want to idle at 10k rpm. Also from what Ive seen and experienced so far with the thumpers, anything smaller than a 50-60 will leave you a little disappointed. My Losi 8ight-T with my 62 on it outruns the 2 stroke it came with in acceleration AND top speed but compared side by side with a .52, theres a noticable difference in power. Displacement is a big deal for these things. Ive never had a 40sc, but I probably wouldnt even waste my time on one knowing what I know now.
Well keep the thread updated if you make progress.

For the handy, you could always convert an existing 2-stroke into a 4-stroke if you have the ability and tools to make a few parts.

Now that's pretty slick right there. That video was just uploaded a couple days ago, too.