I recently finished this kit. Sometimes I do a super detailed chassis. Sometimes I wire up the firewall. Sometimes I run brake lines. But not usually everything on one kit. This was my no short cuts kit. I did as much detailing as possible, using a few photo etched parts, seat belts, after market wheels, brake booster and disk breaks. It came out so beautiful, even girls like it.🤣🤣 I am mostly proud of the paint. I actually was successful with a yellow paint job which has driven me batty in the past. I like the Testors custom colors paints. Some folk complain about it but all they have to do is warm the paint a little and stop trying for complete coverage into coats. It will puddle on you until you learn how to use it. Your car looks great. Just a little filing on the hood latch and the hood will sit just fine.
Suggestion ... measure your wheels in an X pattern under the car, to be sure they are square and aligned, before you get beyond the underbody work. Measurement should be nearly equal on both legs of the X. If not, an adjustment is needed to axle/suspension, you can prevent that set-back look on one side.
Not a big deal about your confusion between the 396 or 427 the same basic configuration applies to multiple engines- valve covers, intakes, water pumps, most external parts are basically interchangeable. Displacement for stock Chevy big blocks range from 396(402) to 454, only a Chevy mechanic has any hope of quickly identifying the difference.