The tunnel on a GTX is quite a bit bigger than an A-body. Looks like some sheet metal work was necessary on this car http://www.moparts.org/Tech/Archive/auto/28.html was I believe was a Dart....just to give you an idea on how much smaller an a-body tunnel is the trans that is in my car fit into an e-body with out any surgery at all.....another 518 swap article into an a-body http://www.hotrod.com/howto/hrdp_0706_hemi_swap/photo_07.html
