MrV wrote:
now that would be an issue but one i would solve by attaching the
tranny to a "GearBox" attached to frame to take thrust pressuer and
that being attached to the prop. kinda similiar to a rear diff

You are trying to say "thrust bearing", I think.

Look over carefully a Soloy Allison fixed wing conversion.

Intuitively, turning a propeller is a smoother load than the diff on a
car. In reality it is not. It took the marine industry twenty or more
years to realize you could use a car ingine in a boat, but only if its
"native" conditions vis-a-vis those of heavy slow turning boat engines
were carefully looked at. Dedicated small boat engines for inboard use,
gas or diesel, have become a thing of the past as autoderivative (with
"automotive" meaning heavy truck as well as car) engines are used
exclusively up to almost 1000 hp today. The LyCon museum pieces have
been saved this fate by a confluence of arcane and arbitrary
certification requirements, legal paranoia induced by Wichita's long
misrule by drunks and bitch-ass widows, and physics-weight is
irrelevant in boats but critical in aircraft, and most autoderivative
engine cores are heavy.