TH400/34tooth sprag questions

I'm pulling the tranny for a long overdue rebuild. Got some questions....I've looked on other forums & sites and am still a little confused.

Background: 350" SBC, dyno sheet shows I put about 300 HP to the wheels. 280 to max 320 lb/ft torque with a very flat curve from below 2000 RPM. 3.36 rear end.

It already has most of a Trans-Go kit in it. Going to put a 2.75/1.57 gearset in it with B&M clutch plates. I'd like to install a 34 tooth sprag (some places say 36 tooth--??) but some places say early (pre-'71 or '69) TH400s only are bolt-in, later ones need a different drum. Other places say nothing about that. Mine is '73.
The gearset is a big splurge for me right now. If it's too much more expensive to change the sprag, well, nevermind. But while I have it apart, "while I'm at it", I'd like to do what I can. Within my budget.

I've started reading the "How to Work with and Modify the TH400" book, but am not very far into it yet. I'll read some more today after chores are done, before I have to go to bed.

I guess my question in short is, can I put a 34 tooth sprag in my '73 TH400 without having to spend another big wad for the drum?

I had to get a 68 or 69 drum when I did my 72 TH400. I forgot where I got a good used one from but yes you have to swap it out for an earlier one. I'm not sure when the change was but my 72 is 100% original so 71-70?

Thanks, Gary. Again.

GTR1999 said:

I had to get a 68 or 69 drum when I did my 72 TH400. I forgot where I got a good used one from but yes you have to swap it out for an earlier one. I'm not sure when the change was but my 72 is 100% original so 71-70?

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What he said. Used ones are not too hard to find either. Find an older tranny shop, or a trans parts store that does tear downs for parts.