Don't know what you mean by "cheap" but I would think a 671 blower would be what you're looking for. You can find this one at goodvibesracing: BDS-671HATT-AL 6.71 BLOWER STAGE 4 POL W/ AIR-LOC ROTORS $3543.00 (list) $2825.00 (your price). Then you're going to need the intake manifold, etc. It gets pretty expensive in a hurry. It's not the initial price of the blower, but all the accessories that you need, from pulleys to belts, intakes, etc. I'd just hang around your local drag strips, car clubs, look through e-bay and try to find someone running a 460-429, who's blown their lower end and wants to sell their blower and manifold. Shouldn't be too much of a problem as there are many combinations and makes you can use on the 429-460 blocks. Are you running a wedge? Anyway just my 2cents worth.
Even if you fall on your face, you're still moving forward.