Weber measurements needed, please...

If you have a Motorcraft electronic distributor now (1978 or later) I'd go with the TFI upgrade. Pdok already described that. If you have an older one you can get a Pertronix Ignitor II and install that or change to a later model AMC/Motorcraft distributor (and do the TFI upgrade) or a GM 250 six HEI unit. You can find the GM unit in late 70s/early 80s (through 84) trucks with 4.1L (250) six. You need an AMC gear (the V8 gear fits) and drop it in. There is one caveat -- if the dizzy body doesn't drop all the way against the AMC block DO NOT clamp it down. It will bind in the oil pump. Some have ground about 1/16" off the end of the shaft, but most just get a large hardware store washer and put that between the dizzy and block.

If you have the 75-77 Prestolite electronic ignition (easily identified by the double chamber vacuum advance) I advise you to replace it with any other system. It was trouble prone, though the problems were pretty much solved and it should be okay now if it's working right. I just don't like it!!

Pdok and I are in agreement on the carbs too. If/when your head needs work grab a 96-99 4.0L head. They have slightly smaller but much smoother cast ports than the more popular 91-95 models. The smoothness makes up for the size easily. I spent four hours just cleaning up a 95 casting, looked at the 99 I got at a deal and didn't touch the ports -- didn't need it. Then you can run a stock 4.0L header and a 1980+ aluminum 2V intake and carb. Can't find headers for the older head that's not expensive. Clifford still makes a shorty header that fits in cars and Jeeps, but that's the only one. For the cost of the header you can get a 4.0L header, header, and valve cover (have to have the VC with the head!), and even have the head rebuilt. you might even have some change left, definitely will if you have a pick-n-pull type yard nearby.

Build the motor for torque and use it! I had to convince a SCCA racer to do that instead of trying to rev the heck out of it. He started running in the upper half of the pack and even winning on occasion once he figured out how to drive it like a big six instead of a four or high revving V6. He couldn't win drag races down the straights, but could pull out of the corners much quicker than the others. Evened things out!

If you have a GM distributor now I'm pretty sure the gear will work. You will need cap and wires for an HEI. The positive wire from the coil has a resistance wire in it that reduces voltage shortly after starting. The GM HEI wants +12V all the time. Use any switched +12V source. The resistance wire is buried in the wiring harness, not real easy to cut out. 

Any of the AMC vendors will have one. Try www.bulltear.com. 

So far good info given. I think I saw you have a 1v carb & intake now? If so when doing a carb change you should also swap the intake for a v2 one. I am sure you would need to go to one with any carb be it a Weber or any Holley because the adapters made only fit the v2 intakes.

I'd use the 32/36 then. The bigger ones are for more all-out performance. There's a reason the 32/36 is so popular! You have to remember one thing about this board -- most of the members are a lot more performance oriented than just driver/restorers. There are plenty exceptions, but the majority are performance geeks who will always advise for the more power producing parts. Just my observation over the last 10+ years of being here...