RPM Drop From Nuetral to Gear

for the popping, you are getting a voltage drop at that rpm at the same time... pretty weird. make sure you have good ground between the block & frame & negative battery terminal. if needed pull off each of them and wirebrush the connection points. also make sure your electronic ign box and voltage regulator have good grounds.

the popping itself could be a lot of things. you actually may need a stethascope to track it down. could be valvetrain, could be intake crack, or 999 other things.

on the timing, i always used the redneck way to get it approximate, i'd advance it until it was top speed, then back it off slightly. (not 10 degrees!) just slightly. i know you are having trouble getting it to idle to adjust but advance as much as possible but not so much that the engine wont start, then back it off just a hair.
you can get fancy with the timing light later.

you could also ask around there may be a mechanic local to you who is good at rebuilding carbs.

the idle problem persists. if it was me... if i had the cash i'd get a good carb. if i didnt have the cash i'd get one of the hp version thermoquads somewhere, buy a rebuild kit and do it.

it's not that hard, i've done a few of them. rustyratrod Rob can give you pointers.

basically you can get a carb soak kit at auto stores. soak it over night; blow it out with compressed air then spray smaller orifices out with carb cleaner (watch your eyes that **** burns real bad... wear goggles for this part)

then assemble everything together. it's been so long, i dont remember. Rob can tell you where to start with the adjuster screws. all i know is when i put mine on after rebuilding she purred like a kitten. i didnt have a lot of money then and the carb rebuild kit was cheap, and the can of spray.

if you have a holley and want to stick with that you can also rebuild it. there is a book about rebuilding / tuning holley carbs. actually probably 999 books someone else may know the best one to get.