Collecting parts for future engine which I plan to use blower and injection. My delima is that I don't know what criteria to use to determine which size hat system to use, Bug or Bird. Eng is 528 Hemi with 14-71. Have run across deals on each size but I don't know which size to select!! What's the criteria??

Call Enderle, Hilborn or Goodvibes. They can recommend the correct size hat for your app. Forced induction BB I would guess a birdcatcher

Bug is for small engines, smaller blowers. With a 14-71 you could even run a Buzzard on it.

If you have the clearance get the scoop high up off the blower case into clean air.

Your choice really is between a Bird or a Buzzard, go with a Bird, a little calmer on the launch of a suspended car.

The butterflies on the Buzzard are 5 1/4" and the vacuum at the top of the rotors tends to try to hold the throttle blades closed at idle, just because of the massive sq. inch area of the three butterflies. You can compensate with a longer throttle arm to get a little better ratio, that's what I had to do on my Shotgun, but you have to give the pedal a pretty good nudge sometimes to get it off idle. Really only an issue if drivability is a factor, but for your combo the Bird would probably work a lot better. I think some of the early Ron's Toilets had a similar issue with the big single butterfly, not a huge deal, just something to consider.