67vette427, I have the keisler TKOII on my Cuda 340 and love it!
I was forunate enough to purchase the "revised" versions and did not have issues with fit.
Mine was literally a bolt-in deal.
I have a 3.91 rear in my car and with the steeper 1st gear you really feel it, not bad in my opinion.
Smallblocks are screamers so when I launch her she MOVES
Nothing is weirder than getting use to the fifther gear. You get on teh highway, car is starting to rev high then you just put her in fifth and she hums along down the highway
Not to mention the top end runs
Would I do it over again? Hell Yeah! I wouod get the new optional Hurst shifter before you bolt-it in to tighten the shifter even more. The stock keisler shifter feels very similar to the stock 4spd shifter.
Good luck!
As for switching to a 5spd..... I am fortunate enough to have purchased a 'vert cuda which Is an auto. which will be nice for the days I want automatic and drop the roof
Gil