If the goal of the 2.4 racers is to try to have 300hp..don't spend $12k when ebay is full of v6 engines with forged cranks and rods straight from the factory for less than $2500 (already with 300hp)
The trick is to stop any modification on the v6 engines.. The only way I am see this happening is a claimer rule.

I even saw a reconditioned v6 for only 2500.

If you want to play.. Build a 2.4 and have them unlimited.(no tech) For budget racers, allow stock v6 with a claimer to keep the $$ away from these engines.