What are these wires ?

[englands 71]

my 350 turbo trans was slipping so I took it out and replaced it with another 350 turbo. Under the truck I found three wire connectors coming off of the same harness leading from the firewall running down to trans area. . The wires looked like they had been tied up out of the way at some point . One has a whiteish / tan color connector about 1inch by 1 inch square , the other is a common small square metal connector, and the other one is a round rubber type , about as big around as a nickel. It is a female type. Sorta looks like the connector on the rear lamp harness .
They run up to the fire wall to the far driver side and plug into two small square boxes. Wire colors are black , green , blue and two brown wires.
I'm not sure if the truck originally had a 400 turbo or not. The drive shaft , trans cross member appears to be factory but could have been changed years ago. Could these wire have been connected to a 400 turbo ?
Anyway I just need to know what they are to be sure something isn't hooked up. I just got the truck recently and I've been having problems with the turn signals , side markers etc. By the way , are the side markers supposed to blink ? I thought they were supposed to but mine are not and the blinkers blink very fast and short. Led tail lights. Thanks for reading.