I have a 1965 Oldsmobile delta 88 with a 394 that needs a rebuild. I have a 1966 delta 88 that I want to take the 425 from and replace the 394. I was wondering if I'll run into complications. Motor mounts? Transmission? Any advice would be greatly appreciated

 

I thought the 425 replaced the 394 in all 65s. Rock auto lists the 425, not a 394.

 

I could be wrong on the original engine. I only got the cars yesterday and haven't picked them up yet. If that is so them I shouldn't have any with the engine swap itself

 

Welcome to the site! When you get the car home post some pictures for us. But yeah, I agree that the engine should have been a 425 in 1965. Easy swap for another 425 or 455 even. John

 

I will post pictures when I can.

 

You are either wrong about the engine or the year of the car. The last 394 was made in the 1964 model year. All 1965 full size cars (except the J88) came with a 425. The J88 got a 330.