No it's not worth it, in my opinion. The amount of money it would cost you to take an OBD1 controlled throttle body injection 350 and convert it into an OBDII controlled Vortec would be expensive, not to mention a decent amount of work... and all for like 50 - 60 horse power and 30 ft/lb of torque?
Keep in mind, you would need to get your hands on a set of Vortec heads, a vortec milti-port injection intake manifold, vortec engine roller camshaft and rocker arms, OBDII computer chip, a GM fullsize truck 1996-1999 wiring harness, an axhaust system that will take 4 O2 sensors (plus two cats), a Vortec ignition system... ugh.
For the money and effort, just buy a crate engine if you want a lot more power, or build a new engine out of the 350 you already have. Or do what I did and pull an engine out of a boneyard truck and rebuild that.
Lol, the amount of money it would cost you to convert a TBI 350 to a Vortec 350 with pretty much all new parts, you may as well just find a 1996+ model Tahoe on the side of the road for a few grand and buy that.