Does anyone know exactly what type of numbers this things flows, Ive tried doing searches but ive come up empty handed.

 

Plenty, the ports are slightly taller than a 1204 gasket, my l98 heads had the same size also. The kicker is here they are that size all the way through, unlike a TPI setup. If you want them to match a 1205 gasket, fire up the die grinder and start port matching. From what I measured a 1206 should be able to be used, but I didn't have the actual gasket and you would have to do a lot of grinding.

So my answer is... they'll flow what you port them out to flow, which should be enough to easily handle almost any big cube SBC. Even pro lightning 242's use a 1206 gasket

 

How would it flow in comparison to say the HSR?

 

Results allways speak louder than flow numbers, there are a heck of alot of fast LT1 cars out there.