since you already have the sbc in there i would upgrade to the 5.3. i was able to round up an engine harness and pcm for 500. i spent another 250 on misc parts to get it up and running.
However the 300 i6 is the best engine that ford ever made.
74 2f engine
i am new to this site. i have a 2f in my 74 that runs great, i am wanting to do a v8 swap in the near future i would be willing to do some trading for a windshield frame and top or an adapter that goes from a 700 to a 3 speed case