I'd like to replace my air pump with just a pulley to eliminate it or can I just gut the insides of mine. It makes a weird sound on startup and I think while driving.

 

I simply removed it all together, shorter belt and plugged the holes in heads. This was on a 76 302ci.

 

Most likely you had an engine with multi "V" belts which made it easier but if the poster has a single multi-groove belt it's not that easy.

Yes replacing the pump with a dummy pulley should work fine but it may be possible, as the second poster mentioned, to just use a shorter belt. But not always.

 

Ended up running a 90.5" belt not a 94" or 97"!!.
Didn't even pull air pump! Removed bottom two bolts and loosened too pivot bolt, moved out of way, and cranked bolt down hard. Put other bolts back in their holes and if there was an issue I'll keep old belt behind seat and bolt it all back up with a few wrenches.

 

The idler pulleys made for Stangs also bolts right up to the 5.0 and 5.8 brackets to replace the smog pump. My 96 E150 van never came with a smog pump, it's got a factory bypass idler pulley.