Having had some experience with 9/1 V-6 motors ASA they are not a cost effective option. 500 plus hp, $45,000 plus 1999 dollars, valve springs every day, refreshed every 900 laps (in ASA every 2.5 to 3 races). There's a reason they went to the gonna save money graveyard in both ASA and NASCAR's Busch series.

I only mentioned it because they are the fastest growing class in Australia, v6 non-wing sprints... 3.1 liters I believe. The engines you mentioned are race breed specialty pieces, these are GM stock stuff.
https://www.youtube.com/watch?v=0cfw716bVmQ
https://www.youtube.com/watch?v=xhDwaFQ8BWE