700 R4 or 200 4R in a 51 chevy convertible?

Would any one have an opinion which is the best tranny for my 51 convertible? I will be doing a crate 350 and M11. Or if there is a sight that I could be directed to for more info on physical size of both trannys. Need to know what will fit to the stock xmember . I would be grateful for any help guys.
Thanks, Dominic
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200r4 is a better fit size wise, it's the size of a TH350....
700r4 is a bit bigger...

 

Actually, I think the 200-4R is slightly smaller than the TH350 whereas the 700r4/4L60 is relatively the same size. I just yanked my TH400 to put in a 4L60 and it is smaller, along the lines of the TH350s I've seen.

 

I "think" I have to agree with Critter...
I don't know about the 200-4R.. But I had a TH350, and a 700R4 testing them for fit in my new rod.... best I can remember the two 350's were about the same size.??

If it helps any... I talked to 3 or 4 guys at the Good Guys show this weekend. They had took out a TH350, and replaced them with a 700r4. All said they gained about 3 Miles / gallon with no other changes.

 

700r4 is 30 3/4" long. TH350 and 200r4 are 27 11/16"
700r4 is 20" wide. Both the TH350 and 200r4 are 19 1/8"
Powerglide is 27 9/16" long and 19" wide.

Width is at the bellhousing....

And just so you know the 200r4 takes less power to run vs. a 700r4.
Same as a 12 bolt vs. a 9 inch....

 

Thanks for your help and advice fellows. it's funny zman, I just picked up a 10 bolt rear last weekend. Than I stopped to talk to a tranny guy on my way home from work Thursday. He tells me he sold a 12 bolt posy rear and the buyer wants to get rid of it. So... I may be doing just that. A 200 4R and a 12 bolt posy under a 51 Chevy convertible. Funny how things work!
Dominic