Engine, auto trans fit

[C.Jett]

1985 F150 I6 auto.C5  will c5 on my I6 fit a 302 ? will driveshaft fit ? Radiator ? Thinking about changing to a302. What do I need ?  CJ

[Gary Lewis]

The C5 should bolt right on.

But I can't say whether the driveshaft will fit, although you should be able to figure that out by looking at the page at Documentation/Driveline/Driveshafts.  The main question will be the length, which that gives you.

However, the radiator won't work.  All gas-powered V8's use a radiator with the inlet on the passenger's side and the outlet on the driver's side.  But the 300 six uses one with the connections just reversed.

And you will for sure need the right perches & exhaust, and probably a few other things like the throttle cable.  You can see a bit of that on our page at Documentation/Engines/Engine Swaps (don't go to the 300 Six To 302 page).  There's a list of things as well as a link to another page on Engine Perches/Stands/Brackets.

[mat in tn]

the foundational difference is where and how the engine mounts to the frame. the L6 has engine mounts that are mounted to unique perches which bolt on top of the main cross member whereas the 302 sits further back and mounts to perches riveted to the rear of the cross member and the frame rails. believe it or not, it sits back about two cylinders worth. the line where the engine meets the bell housing is exactly the same. the bell housing will fit perfectly. the flex plate WILL NOT. being that you have an L6 now are you sure of the trans? is it a c5 or an AOD? best to look at the pan which the aod will say "metric" stamped into it. and also, it will have an extra cable going to the carb for throttle valve modulation. another tell is the shift indicator on the cluster. the aod will not show a second gear setting. it will show p,r,n,od,d,l. some models show 1 in lieu of L.
as long as you keep the trans then all behind it will not change. if you change the trans then all may be affected. there are still differences to consider if going forward with a v8 swap. there are 302s and there are 5.0s. they are not the same!