can some please tell me the difference betwee the 351m and the 400?

OK here's the skinny on Ford engines. Pay attention because it gets confusing. LOL !!! The 1970's were a milestone for Ford and many changes took place in the cars and in the trucks in those years. The 351-C, the 351-M and the 400-M were all the same block but were quite different externally and very little items interchanged between them. Now since you say you have a 1973 F-250. If it's the original engine, I would go ahead and say that you would have the 400 in it as the 351 -M didn't come out until 1975 when Ford discontinued the 351-Cleveland at the end of the 1974 model year and as far as I can remember the 351-C wasn't available in trucks at all. They did however offer a 360 in the F-series trucks from 1974 up thru 1977. The 360 was a completely different block. It was an FE block (FE=Ford/Edsel) and was identical to the famous 390 engine which was also in cars and trucks up to early 1971. Most of the F-250's had the FE 360 engines in them after 1973. Most of the F-100 and F-150's had the small block 302 or the 400 up to 1974 and either the 302, 351-M, the 400 or the 460 after that. The 400 came out in 1972 replacing the FE 390 engine in cars. The 360 replaced the 390 in trucks. .Ford also had a 429 engine as an option up to 1974 and that was replaced by a 460 (same block as a 429) from 1974 and up in all the fullsize cars and F-series pickup trucks. So you have to have either the 400-M engine or the 360 FE engine. The Fe engines intake manifold ran under the valve covers by about 2 inches, the 400 engine did not as the intake was mounted inside of the valve covers. Ford also made a 351-Windsor but it was basically a 302 block and had unique looking valve covers that had a "V" effect when you looked straight at them. Kenny/MrBlueOval.

thanks u very much i do have the 400m but the there was a 360 in the to start a owner changed the motor out to an 80s 400m, i ran the vin number on the truck and it told i came with a 360 and when i went in for a locker i have the ford team run my engine ser # and it came out of a 150 form the 80 witch is fun because befor this truck i had an 81 f150 with the same block

In 1970 ford had a true 400. Not affected by smog laws that took effect in 1971. I am hoping to find a rebuildable engine 1970 model 400.

So, on the 351 & 400m...theres was no mention which engine Ford used in 1979 Ford Custom F-250 4x4 400? I am original owner, find dudes arguing with this ole woman about that!! Laffin. And...would my truck have a 3 or 4 copper or aluminum core radiator in it. First time to replace. Help me