Heh, tri power.  They sure do look cool.  Here's the thing, they won't give you any more power; that was a marketing gimmick from the '60s.  An engine can only use so much fuel.  Giving it more fuel doesn't make more power, in fact it does the opposite, because if the mixture gets too rich power falls off.  The old racer's adage is lean is mean. 

My neighbor was a very influential Pontiac racer in the '60s and '70s. He also ran a garage and obviously had a reputation for working on Pontiacs, so everyone in the area brought him their GTOs to tune and modify.  The ones who would listen he ripped those old tri power setups off and replaced them with a single 4 barrel.  The car ran better, maintained a tune better, and actually made more power.  He has those tri power setups stacked in his barn like cord wood.  Now he sells them off to the resto guys who just have to have them because they keep hearing "three dueces and a four speed and a 389" blaring in their heads.

So my advice would be simple: don't.  Its a quick way to spend $1,500 on something that looks cool, but that you'll ultimately come to hate. 

Your car so do it if you like. I like to see those. I have an Enderle mechanical injector setup I would love to put on a 289 after converting it to electronics. Those eight stacks just look vintage and awesome. Impractical, expensive, yet awesome.