I have a 1979 F-350 with a bad 351m. I also have a 78 with a good 390 and a 400m avail to me for free that needs freshened up. I am in need of pro's and con's what to do.

Thanks Much

 

The 400 would be a direct bolt in. With a small 4bbl and a RV type cam along with an aftermarket timing chain set without the built in retard, it should run pretty good.
The 390 will need the frame mounts to be changed along with the tranny and all of the accessories on the front of the engine.

 

lxman is correct. 400 direct replacement,

 

use the 400. you can build these suckers up now seeing as that edelbrock has a nice intake for you, you carb of choice, and a crane cam. works good!

 

Thanks for all the input a 400 it will be.