While I have great respect for you being the first (and only) to add a corvair to the gmod workshop, it has many flaws that I think will turn people away from it. Firstly, the engine; the model depicts it using a transversely oriented i4 engine, which is very far off from the air cooled flat 6 engine it should have. I won't blame you for that though since you did not make the original model. What you did make and have messed up is the transmission; you made it have 3 speeds when the stick shift on the vehicle model clearly shows that it should have 4 speeds. The power output is also very inaccurate; you only gave it an underwhelming 80hp maximum when the model shows that it should have up to 140hp (as shown on the rear emblem). If you are going to add a corvair to the gmod workshop, please do it right.

Luckily, simfphys provides a vehicle and transmission editor, so I will post my edits to the corvair here:
Gear ratios (taken from page 373 of "Corviar Owners Handbook of Maintenance and Repair"):
1st gear: 0.313
2nd gear: 0.457
3rd gear: 0.694
4th gear: 1.000
Reverse: 0.273
I also managed to find the gear ratio for the differential, which would be 0.282
As for the power output, I set the torque output to 156 with a powerband end at 5200 and an efficiency of 1 to reach the 140hp maximum, but you can increase this value if you want to have the power output of a Yenko Stinger (which has yet to be added to the workshop).
If anyone has any better ideas for vehicle modification, please share.