I6 performance? 1973 250

the 250 can be built to make good power. mustangs and fords had a article where a 250 was built with a turbo and an aftermarket aluminum head and it made 323hp with a relatively mild build. we have a guy on fordsix.com that goes by the user name does10s that has a falcon that indeed runs tens in the 1/4 mile with a turboed 250. so first decide if you want to keep the 250, or go with the 302 ultimately.

if you are going to replace thee 250, then do it. you can put new lifters in to nurse the engine through until you can put the 302 in. but the nice thing is that you only have to replace the mounts, since the 250 and the 302 use the same bell housing.

There is a ton that "can" be done to I6s to make good(or even great) power. The problem is that you will spend far more making power out of an I6 than a SBF...the first question you should ask yourself is just how much power you need for whatever you are using the car for....engine mounts literally take 5 minutes to change out...that should be the least of your concerns with an engine swap...not sure what the base model your rear end is....but for 65-68 its a 7" and a v8 swap will eat it in short order...there are more things that need to be addressed with a v8 swap than just the engine and mounts is what I am getting at

in 71-73 the mustang had the 8" rear end as the base rear end.