Olds engines have slower drain back than some other engines. So what? Actually if you get in the weeds about it, the drainback on a SBO is faster than a BBO because of the deck height is lower so less distance to travel back to the pan. That should save 0.00000001 seconds of drainback time. Someone timed it one time. 
Seriously, unless you're going all out, there's really no reason to run HV on a street-run Olds engine. You said you were building it for street cruising, so you should be living in the lower RPM range (well, in Turna World that means 30% of the time anyway). Especially with a 5 qt. pan, you don't NEED to be using any HV pump. Remember Olds built them stock and unless there were issues of not keeping oil levels up, you could street them all day long without oiling issue problems.
Seriously, unless you're going all out, there's really no reason to run HV on a street-run Olds engine. You said you were building it for street cruising, so you should be living in the lower RPM range (well, in Turna World that means 30% of the time anyway). Especially with a 5 qt. pan, you don't NEED to be using any HV pump. Remember Olds built them stock and unless there were issues of not keeping oil levels up, you could street them all day long without oiling issue problems.
