Taillight swap

[bikenut]

I looked in a few old threads and haven't seen this question asked before...but if it has my apologies up front.

So I have a daily driver 1980 720 and recently picked up an 85 parts truck. I want to swap the bed onto the 80 chassis which of course means running the 85 tail lights. The issue is the running lights work when i plug in the 85 harness to the 80's but not the brake lights. Both use 1157 bulbs but the 80 has another bulb in the lens...one of those small push in types. I looked at the plugs and the 85 plug is a 5 pin and the 80 plug is a six pin...is there a wire I need to connect together or am I asking for a fuse blowing fest? Any help would be greatly appreciated.

AB