Carb issue. Take a look.

Defiantly wouldn't put another carb on it until you get all the "crud" out of the fuel system.

Mechanical secondaries vs vacuum is a debate that can go on for days around here.

This is my personal opinion.....

I would stick with vacuum secondaries for your truck. With the correct secondary diaphragm spring it will do what you are looking for and more than likely return better fuel economy.

Buy this.......

http://www.summitracing.com/parts/CMB-03-0100/