are the cylinder heads on a 225 v-6 and 3/8L the same

I can’t recall the specific year the engine change came about. [ I’d opt for new manifolds that FIT your vehicle ] Hint: the *odd fire* engines had a weird looking spark plug wire placement on the distributor cap - like some wires were next to each other then it would skip a space in the firing order - once you’ve seen this setup - you’ll know the difference. The later years are ported differently as well.