check your grounds!! usually a ground wire issue!

good luck!!

 So the 1157 is the top one and 1156 below it?

I do not have a wagon.  The following is my interpretation of a 78 EVTM and some earlier Pinto manuals and some assumptions on bulb numbers.  The 1157 bulb is the dual filament bulb for stop-turn (brightest filament) and tail light (dimmer filament).  The 1157 should be placed behind the red lens.  The 1156 bulb is a single filament for your back up lights and should be place behind the clear/white lens.  The wire colors should be:
light green with orange stripe - to left hand stop-turn filament (from turn signal switch)
orange with light blue stripe - to right hand stop-turn filament (from turn signal switch)
brown - to both tail lights, both side marker lights, and license plate light (from head light switch)
black with pink stripe - to both back up lights (from transmission switch)
black - ground to all lights (from numerous chassis connections)

Hope above is correct and helps.

It's not even that hard, the single contact on end of bulb MUST go in the single contact socket, the dual one goes in dual socket. You look inside the sockets to determine number of contacts there and same on any car on the planet. The bulbs also have different pins on the sides, they are stepped high/low on dual contact bulbs and in line on singles since the orientation does not matter. So, butchery job if they are transposed since bulb was forced into a socket the pins don't line up with, and how one tears up sockets.

LOOK AND THINK should cure any issues there. Wagon or no. You can't have a 'second filament' for the reverse since the reverse light physically is in a separate position with a clear lens.

If you don't remember then look. Why I mentioned it. The answer right there. The parts ARE clearly keyed. Why I said what I did, don't stay in a mental vacuum........ .............m ost things can be answered by simply looking and thinking. Research is your friend and the internet could make up for no schooling at all for a driven person. The key is realizing the drive factor is in your best interest.

Absolutely no insult or injury intended there at all of course.

Wire splicing in and of itself means nothing unless person doing it was incompetent. I drive a Focus that the main underhood wiring harness was severed in like 5 places after a wreck by fire department that has orders to do so to protect their guys from say delayed airbag going off. I spliced all of them back when I fixed the car and so many I couldn't count. That was in 2008 and car started back up with zero issues and indeed now still runs perfectly.