87 Ck-30 3+3 - Engine/Elect questions

[Cervantes]

Hi!
I picked up an old government 3+3 Ck20 over the winter, and I'm fixing it up as a work truck. Had some questions about it.

As far as I can tell, it's a standard 350 3-speed in there, but I'm not sure if it's stock. There's been some mods to it over the years, and now I have bundles of wires all over, random vacuum hoses that end in screw plugs, a completely dead dash, and some work to do. :/ So, looking for some hints!

- I'm still replacing gaskets, right now I'm set to work on the exhaust gaskets and the tailpipe... but the engine runs rough and takes a few tries to start. On most engines I'd expect to be able to pull out a timing light and twist the distributor cap to fix that... but this one doesn't! How is the timing adjusted?

- The dash is entirely dead... speedo, odo, all the idiot lights save one. I'm slowly working my way through it, think I've figured out what's wrong with the speedo cable where it ties into the tranny... but in poking around, I found a few dashes in some mid-80's suburbans and such that have gauges instead of idiot lights. Seems like I can just pull my dash and tie the new one in without rewiring, is that right?

- The back left light assembly is dead. Turn, tail, running lights all fail. The right side, and the fronts, all work fine. I replaced a bulb on the left and still got nothing... and yet from the wiring diagram, it seems that the wires for the brake/turn/running lights are all seperate... so I'm not sure why just that one side would be dead? So far I haven't found a break in the wiring as it runs to the central line that runs up the length of the truck... I'm hoping someone knows of a "gotcha" on this that'll solve this before I rewire the whole assembly

- I'm going to replace the exhaust... everything from the engine back. I'm aiming for quiet and cheap, but I figure while I'm doing it, I should check on what's best for this kind of truck... should I just run 2 1/2" all the way back, or size up to 4"?

Thanks!
C