My current booster is 9" from the firewall. Not sure on K30 booster length but the Astro HB looks to be close to 6-7" which many off-road guys seem to use like this one on an old Bronco. I know a smaller vacuum booster would be easier. I have to admit I never cared for my stock master\booster performance after I added the 1 tons many years ago.I dunno, I think the master is still out there a fair bit. The hydro-boost isn't a super short set-up. G body boosters are a little smaller diameter, but should still give you enough vacuum to do the job...
I'll have to do some research and see whats the best option for my setup.

