I have a 66 f100 with a tired 352 4 speed. Will a 390 drop in without changing motor mounts and bell housing? If not, any suggestions on how to improve performance with that 205 hp. 352? Thanks in advance to all.

 

352 and 390 are both of the FE engine family. It should be a clean swap. Your mounts, bell housing onto the 390.

That said, what is the problem with your 352?? The 66, 352 is a peppy engine in its stock form. What are you after?? A great running stock truck or seeing how fast you can get to the next stop sign??
Cap

 

I drove these motors in the 60’s and they were dependable but at 205. Hp a complete disappointment in any performance. I’m not looking for a drag truck, just something that is not a no go showboat. If I want performance I’ll drive My 67 Hemi R/T

I had a 62 T Bird with a stock 390 and it ran out very nice. For show I would look for a three deuce manifold to go with it.

 

Ford replaced the truck 352 with 360-390 in '68. The 390 was more powerful, but still a truck engine, designed for torque and low geared, it did not have the Thunderbirds performance.
A 390 is a great basis to build from, but don't expect much from a stock truck mill, especially a 72-76 one.

 

I’m looking for a 60’s 390 motor. Mid 70’s are all de-tuned

 

Just a couple curious questions. 66 truck is 58 years old. Possibly could not have it's original engine. Any check of the # on the intake manifold beginning with a C=the 60's or D= the 70's and next digit would be the year? Remember, you can't tell a a 352, 360, 390 by looking at it. # On the distributor, hard to see as it face the carb usually, might correspond with the letter designation as to specific engine's it was used in.
Cap