can anyone tell me the correct length the drive shaft should be for a th400 with a 350 motor.thanks

You are looking for the same length as the 400 / TH400. (Turbo Hydramatic - 49.30 inches.)

thanks,one more part i have to hunt down

If you have your transmission slip yoke, know what pinion yoke you have in it and (I'd double check) a correct length, you could have one made at a driveline shop. It wont be original, but will be every bit as effective as you could ever want.

How about this one:

http://cgi.ebay.com/ebaymotors/67-6...QQitemZ4632953998QQrdZ1QQsspagenameZWDVW

I would never trust from an unknown location a used driveshaft. It may cost you more to balance and straighten, then it would to install new.

I had a driveshaft made to my exact length necessary, balanced, and new yokes both sides, for $185 bucks. Money well spent.

You have a great source for custom driveshafts. The same one made locally in my area would cost over $400.

You can check with them at www.powertrainindustries.com and they will talk to about it should you need to. They have a location here in town and have a number of the small parts as well.

where do you measure the drive shaft from?center to center on the yokes or edge to edge?

center to center according to AMA specs
http://firstgenfirebird.org/firebird/1969/ama/ama_index.html