71 C10 backfiring and loss of power after changing distributor

[tino0217]

I have a 71 C10 350 small block found out I had a short in my aftermarket tack ended up changing my distributor, module, and coil now that I've done that it's backfiring and there's no power when I get it up to 30-40 mph. I have retimed it at 12° past advance I've checked all the spark plug connections to make sure they're tight I have noticed where the vacuum connects to the distributor cap that the cap is leaning and I can't get it to fit any tighter but it is on tight and when I did do the timing I did plug up the vacuum hose I have adjusted the gas air mixture on the carburetor which is your typical four barrel Edelbrock. Before I realized I had a short the truck was running perfectly fine. Now that I've gone through all the wiring to see if I had a short because my stupid parking lights weren't working this occurred and I couldn't get the truck to start for no rhyme or reason that's when I started to look for a short in the wiring and found out it was in the aftermarket tachometer. Any ideas what I may have missed I would appreciate the help got to get this puppy back on the road.?