Firewall tag and engine code, please help

Can Someone Please Help Decode This And Tell Me What I Have

Hello all, I am trying to decode the numbers on my firewall tags, they are

12 Detriot Michigan
ST 65 13837 Body BF 3536
TR 714 E Paint KKA
ACC A49 B70 15381

I know the engine is not original because it has a 454 in it, but the engine numbers are
GM T12
3999289 and on the other side of the fly wheel area it looks like ( L 4 either 78 or 73