conversion from six to 8 ?

You need everything you can buy my 1970 Sportsroof v8 car for $3,000 .

To do it right, you will need engine, tranny, motor mounts, transmission crossmemeber, drive shaft, rearend, front springs, front disc brake conversion, radiator, wiring, exhaust, etc... just about everything

depending on how much power your 351w is going to make, you can strike the trans and the rear end. mustangs with the 250 got the 8" rear end, and the bell housing will bolt to the 351w. you will need the proper flexplate/ flywheel for the 351w depending on the transmission. the crossmember is going to be the same, as is the drive shaft. if the car has the C4 it will handle the power of a stock or mildly built 351, but if you are going to make more than 300hp then upgrade the trans to V8 specs. you will need to upgrade the springs in front if you want any semblence of handling. is also recommend the disc brake upgrade. as for the wiring, you can use the stock harness, but some wires you will need to extend.