In addition to the ford case there are 2 versions of the chevy case. The early model was for a 12" flywheel. Then they went to the 14".

Do what picklenjim says, take to a local shop but make sure they have the manual - there are a couple of things that are not obvious when working on them.

Great ! Now I understand. My flywheel is 14" and my new tranny is for a 12". Itīs only a difference with 2 mm on the inside diameter so I think I will try to mill the new tranny so it fits before I try to replace the parts inside. I will let you know if I succeed. // Carla

Hey thanks for the heads up on that Marc. I never realized that before but knew I had a case on the shelf with the one hole not drilled. Compared it today to a newer one. I measured the opening and it appeared to be 1/4" larger. You can actually see that the cases with the larger openings have been machined and the smaller ones are not.

Carla .... On mine I measure about a 7mm difference which would mean it will need 3.5mm removed all the way around. Also you should drill out that missing bolt hole.