I have a 1968 oldsmobile cutlass s that originally came with a 3sp manual tranny and I have two options (a)a B&M built th350c w/ locking torque converter and 220 stall converter from a '81 corvette or (b) th400out of a 1970 delta 88....I wanted to see if any of yall know if that th400 is probably a longtail therefore, I will need to cut my driveshaft is better or use the corvette th350c and buy the bellhousing adapter and buy the lockout adapter for the torque converter lock. which would be better? I have to either buy this th400 out of town or just use theth350c i've got right now.

 

I can't tell you if either of them will be a straight bolt in, but my hunch says no. The long shaft is a no go for sure and I have no clue as to the length of the 350C vs the 3sp.

Also keep in mind that all of those stick shift parts are worth money. Your crankshaft especially because automatics were not drilled for the pilot bushing.

You will most likely need a new driveshaft. I wouldn't mess around with trying to have an almost 43 year old shaft cut and rebalanced. It's just not worth it. I had a new one made last year for $300 including the yoke.

 

One more question bud, if that th350c's length is good have you heard anything bad about the aftermarket torque converter lockup switch by b&m? I know I would need it if I use that th350c since my car was originally a standard and non computerized.

 

Most of those aftermarket pieces are pretty good. B&M has been around for a long time and from what I know of them they stand behind their stuff.

 

the th 350 and th 400 are the same length bell housing and all just went thru this swap in a 75 olds was a straight forward blot in replacement and gained the advantage of the heavier duty tranny

 

No it's not a " bolt in replacement". A TH350 is a different animal from a TH400. Not only are there varying length tail shafts on both transmissions, but they use different yokes. Then there is the placement of the crossmember being further back on the TH400 and this causing the use of different length parking brake cables.

 

the tail shaft off the turbo 350 will bolt on to the turbo 400 if the tail lengths are different the turbo 350 and turbo 400 are4 the exact same transmiision with the difference of clutch matterial and the cogs and pump pressure and thats the plain simple facts bud just yoked a turbo 400 out of a chevy nova slid it into the th350 case and i drive the car daily and before ya tell me i dont know a thing just google MrCs 75 olds and i drive it daily so funny it fit with no issues

 

Dude I know what I'm talking about. I've been doing this for 25 years. The TH350 and TH400 are not the same transmissions. The yokes are massively different in size.

Look at this link from Denny"s Driveshaft showing the differences. http://www.dennysdriveshaft.com/c75_general_motors.html

There is a possibility that you have a TH375. That is a TH400 case with a TH350 output shaft.
But by no means are the TH350 and the TH400 "the same transmission". You do your research before you go spouting on about what you know nothing about.