I woud like to replace my 300 6cyl. with a 390. My transmission I believe is a 1969 4 speed, I think it is a T18. What do I need to match the 390 with my current 4 speed?

 

Probably just a diferent bell housing. You might also have to move the crossmember a few inches to compensate for any change in legnth.Make sure the I.D. of the pilot bushings are the same. If it's a divorced t-case you may have to have a new drive shaft made. I wish I still had the t-18 from my old 70 f-100. I like the spread between second and third a lot better than on the New Process box.

 

the 390 will also need non straight six engine perches for the frame, the engine will be too far forward otherwise

 

If I remember correctly today, ( CRS disease, ya know....) you can use the six cylinder perches, but you have to move them. DF

 

I just changed my 240-6 (same block as 300) for a 360 (same block as 390) Easy change. Moved 6 cylinder perches to the rear position. Bell housing came with 360 and way different than 240 bell housing. Best change I ever made. My 1969 F-100 now pulls 4 tons of hay without a problem while the 240 was SLOW.