rebuild my 351m or just buy a new one?

[classictrucknut]

i have a 1979 f250 ranger 2 wheel drive with a np436 manual 4 speed. it runs good and has plenty of power and if my uncle (previous owner/ idiot) isn't lying again then this engine only has 58,000 miles on a rebuild but i just had to replace the fuel pump and in crawling around under the hood it looks much older than that. would it be easier and more cost effective to rebuild this myself or try to find a new or freshly rebuilt one somewhere? also if anyone has a 351m for sale let me know because i cant find any good ones here to buy. i think i want to get a new block and just start from scratch and then drop in a complete engine as my truck is my daily driver. also i am looking for a good running 73- 79 f150 or 250 with a solid 4 wheel drive body doesnt have to be great

[JockD]

I owned a 351M-powered 1979 F250 4x4 for years. While it had enough horsepower, it didn't have much torque, which isn't the best for a pickup. The 400M is essentially the same engine with a longer stroke crankshaft, and puts out much more torque at around 2,000 RPM, which is where you need it in a pickup. Mu suggestion is if you are replacing the engine, go for a 400M.

[Kuskoal]

i second that opinion, 49 cubes (351 to 400) works pretty well in the same block without hurting anything. You cant tell if it was rebuilt without looking into the engine, grease has its way of saying "old"