Welcome, and gratz on your new acquisition! Here's a good thread of advice for new owners:
http://www.mightyram50.net/vbulletin...and-do-it-ASAP

Count your blessings that the stock Mikuni carb is still working well for you, only a matter of time before it starts misbehaving due to age-related failure of some component or another, so you may as well start reading up on the popular Weber carb swap, plenty of good threads here about it.

The stock Mikuni is based on a fairly ancient design originally engineered for performance more than economy or emissions, so as regs and market demand tightened around those latter aspects, they just kept tacking on ad-hoc modifications and various add-on gizmos to satisfy them, which of course just means more points of potential failure in the long run as the truck ages. Rebuilding the Mikuni is pretty challenging, not for newbies or the faint of heart, so unless your area has emissions inspections that require all-stock equipment, a Weber swap is just the ticket for resolving most stock carb woes.