A little bit of "Transmission 101" about how the Corvair transaxle was made... pretty clever use of high-volume front-engine rear-wheel drive parts.
Take a look first at the conventional layout labeled "Nova" below. The same Saginaw 4-speed (or 3-speed) was used in this fashion in just about every car GM made in the '60s and '70s, even some Corvettes. I tore down and inspected several of these every week in QC after production was moved from Saginaw, MI to Muncie, IN. Never did put 'em back together... the parts went back to the assembly line despite having a a few hundred miles on them.
Note the input gear (red), typical of most RWD transmissions... it drives the cluster gear (green) at a small reduction to get part of the reduction out of the way (this allows more reasonable gears at the next step). The cluster gear then drives whichever speed gear (1st, 2nd, or 3rd) is locked to the out shaft (blue). For 4th gear the input shaft (red) and output shaft (blue) are simply locked together.
For the 1961 Pontiac Tempest, the same gearbox was moved to the rear by splitting the input gear, extending it with the world's most expensive driveshaft (8660 steel, carefully heat treated and every one Magnafluxed). It was 3/4" diameter and flexed in a long curve (almost 4" dip) going through a couple of guide bearings. The only other change was the shorter output shaft with splines that engaged internal splines in the hollow pinion shaft in the attached differential housing. A swing axle rear suspension completed the deal. This whole layout was the brainchild of some guy named John DeLorean.
The Corvair used the same Saginaw gearbox and the Tempest differential housing but the input gear had to come from the rear. So both the pinion shaft and the gearbox output shaft (blue) are hollow... and the (24" long) input gear shaft (red) runs through them. Note that the gearbox is still facing the same direction as in th Nova and the Tempest... AND all the components inside are still turning the direction they designed for. Note also that the Corvair crankshaft is actually turning the same direction as the Nova and Tempest
in the car (i.e. clockwise when viewed from the front of the car) but is considered a reverse rotation engine when viewed by convention.
The Crown (Ted Trevor) Corv-8 basically just left the Corvair transaxle where it was and put the "Nova" bellhousing back on the front of the gearbox and put the "Nova" input gear (red) back in it. Simple, strong, everything still rotating their original directions. Cramped the driver's seat a bit though, as I recall.
The Kelmark kit simply turned the transaxle around and used a bellhousing adaptor to attach the V8 in place of the Corvair engine (the transaxle was not flipped upside down as Clark Corvair claims... hate to contradict the 'Vair experts but I'm very sure of this). Due to the details of the adapter, a new input gear shaft, 7/8" longer than stock, was supplied. Seems a shame... I wonder if they intentionally did it that way to supply a higher quality shaft. Anywho, this layout has the potential shift quality and strength disadvantages of the gearbox internals and ring & pinion all running backwards. Seems they got away with it though. I used to stop by Kelmark once in a while to see what neat stuff they were doing when I was going to college in Michigan, starting when they were
still operating out of a service bay in a gas station (in Okemos?). Anybody remember their sidewinder V8 transverse transaxle? I recall the prototype... don't know if they ever manufactured and sold any.
If you do flip the Corvair transaxle upside down, you could bolt the Corvair engine (or one of the many reverse-rotation Honda engines) back on (with a thin adaptor plate to right the bellhousing bolt pattern) and everything goes the right directon, it's mid-engine and low engine CG. Not sure about ground clearance; the 'Vair engine might not work; the Honda might need to be dry sumped?
Closer view... Note that Tempest
layout (minus the Rope Drive shaft) is exactly what is used in the current Corvette. Straight through (input gear locked to output shaft) is still 4th gear... two more speed gears (both overdrive) added for 5th and 6th.