Need help wiring

[z3pr68138]

I own a 1987 Chevrolet K5 Blazer 4 wheel drive, 5.7 auto, ... pretty much factory original. A little over a month ago I was hit out on the interstate at 50+ mph. Insurance paid, body shop did what I couldn't. Opted to have new lower quarter panels instead of painted. I found a 1990 GMC Suburban being parted out. I bought the front clip and both front doors. Currently on my 87 K5 Blazer. Anyways, the 90's headlight wire harness does NOT simply plug into the 87's firewall. I either need too cut and splice or need a adapter. Anyone solve this problem ?? Details and pics if you have them. Thank you.