Run for the hills. I blew my tranny out last year in my 67. It has a TH400 from a 68 and a 400 from a 68.. I pulled the engine and tranny, dropped it off at the shop. Had it rebuilt to handle 1000 HP and added a shift kit. Cost $1142 out the door.
$3500 is highway robbery. 2 hours to get the engine out, 3 to put back in. Nice B&M rebuild kit is $230.
1957 Thunderbird 289 1967 Firebird Base 461 1968 C-20 327