I bought a 67 ford mustang with a 351 cu in Cleveland engine. How hard would it be to take it out and drop in a mustang straight six that i have? Would it require any crazy modification or wiring or something like that...
Some one put the work into transplanting the 351 into your 67 that never came with Cleveland's. To do this transplant right required front springs, spindles, brakes, cooling system, motor mounts, trans, cross-member and trans mount, drive shaft and matching yokes, rear axle and leaf springs.
It seems like a shame to move one of the most sought-after Ford small block V8s for a rather ordinary 6. If your Mustang came with an automatic, you might want to check if the FMX automatic is compatible with the low-protein 6.
If you are not technically adept then leave it alone. The transmission is probably different. That said, a car that old is not hard to swap engines in. They don't have all the confusing electronics and computer controls.