If you want to step up to larger throttle body, there are ways to keep them from becoming "twitchy" and from being like an off/on switch.
Check outthese Vortec t-bodies. As you can see there is a 1/2 moon shaped device that is specifically designed to prevent such scenarios. The Vortec 4.3 has a bigger 1/2 moon device than teh Vortec 305/350 t-bodies.
The 305/350 t-bodies are 75mm, IIRC the 4.3 t-bodies are smaller at 65mm, but I may be confusing t-body size with MAF sizes.
Forced induction is very sensitive to air restriction on such through t-bodies, but not as much with blow through t-bodies. If this setup is a suck through t-body mods or upsizing can make dramatc diferences.