transmission Yoke
 

Any reason a trans slip yoke from an 81 th350 will not work with a 78 th350 car? Spline count and joint type look the same, I just want to make sure Im not missing anything.

Should work fine. Just ensure that the width for the u-joint (1330) is the same.

thanks. what is confusing me is that I am seeing 32 spline listed on most websites for a 78. mine is a 26 (with a gap where 27 would be). Did my trans come out of an 80-82 car? it is a lock up 350, so i suppose that would make sense (non lock up in 78..correct?)

32 spline is for standard trans, 71-81. 77 was the last year for 32 spline automatic, 400 trans only. All 350 trans are 27 spline, 76-81. 82 vettes were 700r4 only.
Mike

Thanks for the info, Ive been trying to find that exact details! Thanks!

Your welcome.
Let me add this:
80-82 automatics use a 1310 series u-joints front and rear as Larrywalk mentioned. Your vette uses 1330 u-joints front and rear. An 81 350 slip yoke won't work in your vette without using using a 1310 to 1330 conversion u-joint.
Mike

Well, Im not sure what this set-up came out of, but what I have now are the strap type u-joints (This is 1330, correct?), and NOT U-bolts. Also odd, my initial measurements have the driveshaft being just a hare of 28 inches if I get from the center of the hole, 29.5 if I measure all the way to the end. I would love to just measure everything up and see how much distance is between the trans and diff, but the engine/trans are still out of the car. Obviously I have a grab bag of parts from various places here (bought the car with a pile of parts, trans and drive shaft were in it at the time though). Just trying to make it work...doesnt have to be factory correct, just safe and functional.

Only 63-70 1310 u-joints used the u-bolts and nuts. Starting in 71 they used straps and bolts on all the driveshafts. If the bolts for the straps use a 7/16 socket then they are 1330. The 1310 and the 1330 u-joints both use the same cap but the 1330 is 1/2 in. wider than the 1330. I can't help you with the driveshaft length. I'll be tearing down a 78 this weekend for a complete driveline overhaul and I can get you the length then.
Mike

More good info! I'll check the bolt size in the morning.

Well I havnt had time to do much with it, but the bolts are 7/16 heads. I have an 81 yoke on the way, Ill just have to get a conversion joint (looks fairly common). What bugs me is having to wait until I get the trans back in it to verify the driveshaft is correct.