TH350 pours past front seal

Just picked up this 76 nova, and it had a very bad leak past front seal.

I replaced the seal, and it still POURS out past the seal.

???

Ok, so I have two other TH350s at my disposal. One is behind a pontiac 301 so I am assuming it won't bolt up to the straight six in the nova. The other is behind a 305 in a firebird, so it is a chevy bolt pattern, but will it bolt up to the straight six?

Did you replace the bushing behind the seal???..If not that's what is bad, the convertor wobbled, and made the first seal fail.