I just installed an Accel BluePrint HEI, in my truck, last Sunday. I already had an Accel Super Coil on the old distributor, so I just moved it to the new one. I priced the unit on line at Jegs, for $139. I went to Advance and they had it priced at $199, but met Jeg's price, plus no shipping. Paid for it on Friday, and got it on Sunday.
If your engine runs that well, and you're asking about an HEI, I guess you're running a points-type distributor. I have no doubt that an HEI unit like I mentioned above, will be far superior to your old distributor. You'll also need a coil, and a new set of wires for the HEI cap. You'll also need to revise the wiring that feeds the distributor. An HEI needs an unfused, ignition-switched 12V to operate properly. The power to your coil is fed via a ballast resistor and doesn't get enough voltage for an HEI.
www.wiringharness.com can build you a new harness for your truck, with all the right connectors and stuff that you will need to run an HEI.