4 to 5 speed.
If you're crunched for time and space, you can struggle from underneath-
I prefer to take the time and not kill myself in the process whenever possible.
I selected, ordered, and installed a Keisler TKO600 5sp kit years ago and couldn't be more pleased.
Since I gutted most of the car (body on), I planned on a slightly modified 350 of around 425 hp to lead the way.
To Keisler's kit, I added a Sach's 11" pressure plate, disc, roller pilot bearing, and a Keisler bellhousing. Mounted a 30# Hays flywheel on the crank. It's a heavier flywheel than many run but the weight has not been detrimental to my results.
My TKO is the .64 OD and added the factory-looking shifter. I have the equivalent of a VB&P suspension with Steeroids r&p. I changed the rear gear ratio to 3.55.
The last calculation that I considered was making sure that my rear wheel height was at 27", which I've read is the factory tire height on these early C3 cars. I got close using 18" wheels and a 285/40 tire size. They measured at 26.9" tall and was close enough for government work.
Now, when I cruise the car down the interstate, I see this:

I'm enjoying an average of 20.5 to 21 mpg and allows me to range far away from my home base, without any real worries. Afterall, it is still just a Chevy with tried and true components.
Hope that helps and let us know what you decide. Good luck.
The Best of Corvette for Corvette Enthusiasts
It helped that I'd already paid my debt to society, as it were. No outside influences over the "usual and customary" debt that a majority of us carry.
Like the actor Rob Schneider likes to say in an Adam Sandler movie: "You can DO it!".
I can shift so much faster than my worn Muncie.
I have a TKO 600RR (0.82) with 3.55 gears and it's great
You'll want your first gear ratio, (1st gear x diff ) to come out around 10.
Mine's 2,87 x 3.55 = 10.2
The car feels (and is) so much faster, and cruising is so much nicer, sometimes I put in in 4th on the motorway to remind me what it used to feel like
....then straight back into 5thIt helped that I'd already paid my debt to society, as it were. No outside influences over the "usual and customary" debt that a majority of us carry.
Like the actor Rob Schneider likes to say in an Adam Sandler movie: "You can DO it!".
It had been stored for years after it fell into disrepair back in the days before there was a place like the internet to find opinions and assistance. Oh and great companies that re-make the parts and pieces to keep them on the road... They got cheap to keep again. He got it slightly used, but as a kid, I remember his repair costs 'back then' being off the hook. Prohibitive, for Johnny 6 pack with 4 mouths to feed.
Though not my first choice for a project car, (face it, the C3 requires a 'special taste' as the [78] does not exactly turn heads, silver anniversary or not.) and being that he could not get even close to a decent price for it, downsized everything and had no place to store it. So it eventually hit my garage floor and I have been slowly waking her up from her long sleep. I actually got it a point where I could drive it last summer; but it's just not a practical car for the times 'we' live in. It will be once I get a decent cam in it, modernize it, sell off all the nonsense and fluff and get that extra gear or two installed.
He is happy to see it back on the road and I'm glad he is here to see it. He loved that car.
What rear gear was that photo taken with? You'd have to have a 2.73-ish gear to tach like that at that speed.





The 63 has 27" tires and 3.73s. 1700 RPM @ 60. Its got a solid lifter cam and pulls 5th gear nicely.
Oh....and YES pull the motor.
Last edited by DucatiDon; Apr 11, 2013 at 08:41 PM.





I remembered stock as 30# but some guys like 'em to be lighter.
3.55's. Took the pic on level ground while traveling on I-25. It does increase rpm slightly when I'm pulling a grade.
The tach is a replacement and I installed it without any further calibration. I expected the GM supplier (authorized GM replacement parts stickers on the box it was shipped in) to have handled that. ?
I remembered stock as 30# but some guys like 'em to be lighter.
3.55's. Took the pic on level ground while traveling on I-25. It does increase rpm slightly when I'm pulling a grade.
The tach is a replacement and I installed it without any further calibration. I expected the GM supplier (authorized GM replacement parts stickers on the box it was shipped in) to have handled that. ?
Regardless, check this site out:
http://www.angelfire.com/fl/procrastination/rear.html
You should be around 2100 at that speed.
Trans works great with the 3.08 rear gear.With 6 speeds you can always find the right gear and the rpm's don't drop off as much as a 5 speed.
The Keisler speed analyzer for the TKO and plugging in my numbers is close to the same report as procrastination's analyzer.
http://keislerauto.com/speedanalyzer.html
I bet my configuration just fell into a YMMV dimension?
My previous response stands though; highway speed steady, rpm's down, mileage up, car owner happy.

















