which engine did the 69 come with???351w,390,428 were the only opts. the boss 429's were sent to karkraft to be modified for the 429 boss. but there is so much more hp. you can wring out of the 385 series.ihave a 494 in my galaxie with 4-speed and you can go up to 815 cid on the block if you have the money.if you want to make money out of the mach 1 restore it,you'll get more for it. most of the machs have been modified in some shape or form. by the way the 494 is a "can-am" engine used in the early 70's.alum block and heads,but i have regular police heads from 1973,milder cam and offy intake with holley 3-barrel.