Marcos Maniacs

Read some old Wiki articles saying certain engines made the 1600/1800GT a bit nose heavy (perhaps iron block engine). As later Marcos had Rover 8 cylinder, did this make it evebn worse---or were Rover 8 cylinder cars not the same as 1600/1800?
 I bring up these questions because I wondered if anyone had a experience or thoughts on placing a Ford or Chevy V-8 into a 1600/1800GT (something like a 289/302 Ford or a 305/350 Chevy).  Would these engines make the car too nose heavy and ruin the handling? 

I was dreaming about a way to make the 1600/1800 GT more powerful, sound great, have a modern engine anyone can work on....but not at the expense of handling.....

Figured some MArcos had Ford as well as GM engines, so thsi idea shouldn't be too blasphamous  :)