Found two sets of 502 heads om the cheap. thinking about bolting them on my healthy 454s with matched intake. would it work or would I need lots of other teaks to make 500hp

Without knowing what heads are on it now or what you are starting with, no one can tell you.

You saying healthy 454 as already had some work done or in good health?

in health ....good compression and no oil burn
might have room to change cams in front of engines in place .... how much room do I need to swap a cam?

454 mags already have the same heads as 502 mags.

As mentioned we need more info.

REALLY, maybe you should let it be

I am not going to say that you CAN'T change a cam with the engine in the boat, but it would be ill advised. The oil pan needs to come off in order to get the timing cover off to do it properly. It would be nearly impossible to get it sealed back up otherwise.

Gotcha. Thanks

also, the different gen's won't interchange on some, can't put gen VI on mark IV

Thanks guys. Pretty sure I have Gen IV non Mags. I will keep looking for affordable aluminum heads

My friend did both cams in his supercharged 454s in a 42 fountain. No issues. Most boats don't have enough in front of the motors to slide cams in and out.