can you use aluminium heads and intake on a 302cid cast iron block

Yep, an even bigger problem than the lower compression is the larger squish/quench distance which you like to keep at around .040" - .050" to avoid detonation. Back in the 70's they did all kinds of dumb things trying to control emissions.

 

ok well if i get a newer engine (86 and up) what will it need for it to work in my 74 maverick?

 

Basically in a nutshell, everything from the orig engine excepting harmonic balancer, heads and block assembly... This includes oil pan and pickup, front cover, fuel pump eccentric as well as a steel geared distributor to match the steel roller cam shaft... If automatic you'll also need a 50oz balance, 157 tooth flexplate, this will be a aftermarket piece but readily available... A new timing chain set and oil pump would be a good idea...