Looking for 360 advice on a budget.

I respectfulllly disagree because the expense of purchasing Magnum heads, vlave cover and gaskets, rocker gear and new length pushrods add's up to an expense not needed on a budget build period and will create money spent that could otherwise have been used to upgrade what he allready has.
Also, unless this build gets up in HP, reuse of the head blots is exceptable.

The lifters mostly picked up in Mopar cam and lifter set are AMC lifters anyway, so the expense is moot there.

Hence the word budget, not build on the cheap.

Your $500 expenditure could very easy roll right back into the stock head with new racing valves as well as some basic bowl porting to boot.

All the valve gear would be purchased new anyway sinc changing the cam would require new springs. He can reuse the stock retainer and locks no problem.

A Magnum head swap is very close to "A wash" IMO

The 1.5 vs. 1.6 ratio is something that can be useful or, you could just purchase the right cam to begin with. IF it is not on the shelf, Comp Cams and other manufactures will be happy to custom cut one for you and that is cheap stuff to have done.