I'd say that if you already have the chevy engine, use that...

If you wanna use the engine later on in another car, -use the chevy...

and paint it pontiac metallic blue if you ask me

But if you know that you wanna stick with the firebird, it's maybe a bit more expensive (compared to chevy parts-prices) but you can still use all the pontiac stuff...and looks factory..

And just so you know, you can easily use the steeringpump and pulleys from your pontiac, but you will need different brackets...

-the chevybolt pattern vs. bop pattern can be bought for about 50 bucks.. or you can make one yourself..
You can install a mechanical fuel pump on any sbc, and the fuelpump is placed in the front of the side of the engine (passenger side)