Nothing wrong with a quick build. Believe me, you're not the first to get the pistol grip backwards, and I bet you won't be the last. If you're not a Mopar guy, it's easy to get wrong. Good looking build.
Steve, first let me compliment you on your build, it looks really good. Would you mind telling me what parts and pieces you used from each of the kits you mentioned? I had a 1990 Formula that I'd like to reproduce. Looking at the three kits you mentioned (on ebay), I see the '85 TA would supply the rear spoiler and the '92 the wheels and the body. I can't see what the '91 would supply though. Finally, where did you get the front bumper? Modify the '85 perhaps? Thanks for any info you can provide.
For better detailing, you'll want to paint most parts separately, then remove paint as necessary to glue and assemble them, which it looks like you've figured out on your engine. There's always exceptions, and if you have questions about how something should look, use Bing images (or some other search engine) for research.
It looks like you have the carburetor mounted on it's side. Look at the instructions closely and see if you can tell how it should be installed. Unfortunately, the part drawings in kit instructions are usually not very detailed, so it's easy to install something incorrectly if you don't know how it should look already. Here's a pic of a big block in a '69 Camaro to give you an idea of how the carb mounts.