Back to the original intent of this thread.
You mention your 3-53 engine has an SAE #4 housing. Depending on what transmission you choose you might have more luck with a SAE #3 housing on the engine.
Original 53 series flywheels that fit automotive type clutches are sometimes hard to find and when you do they are usually SAE #2 or #3 size (possibly always, not sure).
It may be possible to modify one of the hundreds of different other 53 series flywheels to fit a clutch suitable for your new application, but it's generally easier to do conversions with ready made parts and avoid machine work when possible.
Before getting to far into wrenching on your conversion start trying to plan dozens of steps ahead in an effort to sort out as many of the big issues before they're actually issues.
