Well, I have another idea that could help. Holley makes a TBI to Quadrajet/Holley 4 barrel adapter plate, Holley part # 17-41. There are options for intake manifolds for the oval port heads, I'd use an Edlebrock Performer intake manifold for a truck application. Now the next idea I have would be to get a Chevy 350 TBI system. Then have http://www.turbocity.com
modify the 350 TBI with a larger throttle blades to increase air flow. Then get the Chevy 350 TBI computer PROM chip recalibrated for the 454. It's still not cheap, but affordable.