the 300 I6 even being a really good engine, it won't fit in a Falcon. it's not too long, it would fit that way, but the intake comes over too far and will not fit due to the shock tower.. '69-'70 Mustangs they will fit in, but there wider..... best bet if you want simple, is the 200 I6, or even a 250 if you don't mind changing transmissions... D7 up cylinder head, 2bbl carb, 2.3 Tempo 4cyl flat top pistions, shave cyl head .040 and run a .045 thick head gasket.. that will get around 9.5-10:1 depending on what everything ends up.. 200 hp is not out of the question.... when you figure the weight savings of the 6cyl ( the 200 6 is only 325# ), and the fact you don't have to change spindals, steering box ( if your doing it right, a V8 conversion uses a V8 box ), rear end ect to use a V8.. a 200 will make cheaper Hp as there is no conversion nessasary.