Best way to ID transmission

[DEMONIAM]

I've inherited a 1976 c10 short bed, but have not done anything to her in my few years of ownership. I finally got her to crank, but noticed that the transmission seal had burst/leaked. Ready to order a kit, but I have no history on the truck (other than the engine was "replaced"), and no history on pre-90's mechanical work. Is there a way to identify the transmission, before ordering a seal/filter kit? I can grab pics later today.

 

[73c20jim]

Shape of drain pan.

 

[Arkansas_V8]

You must be registered for see images attach

 

[DEMONIAM]

fantastic, THANK YOU!!

 

[Poppy 87]

If the vacuum pipe is routed to the side of the case near the fluid filler tube, it's a TH400, if the pipe is at the passenger side rear corner of the transmission case it's a TH350



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