As a guy whos already has too many cars, listen up. There is nothing wrong with doing a plain regal in to a blacked out ride. Doing just the outside would only require a grill and painting the trim. The hood can be done later and the rear wing is easy enough. The interior is what sets a GN apart from a regular regal. The 2 tone color of the interior was only done on a GN. Every T-type was one color as well as the regular regals. If this car is solid enough to use the chassis and sheet metal, go for it. This will allow you to make your own car. You will not be stuck with asking yourself about mods that will hurt collectability. You will be able to do what you want. As for your choice of drive train, If you watch the for sale thread, you will find motor/trans/harness deals for 2500 -3000 every now and then. You could pick one up when ever you save for it. I am looking for a plain regal myself to mod the hell out if. Roll cage, frame notch, trick suspension, custom interior, etc. The sky is the limit. I would never do this to my GN, but a reg regal, look out.
GO FOR IT.
Coach