If you run a ST170 bottom end with a black top head, use ST170 valve springs and a 1.8mm frs head gasket it’s been proven at 300bhp

That is top end but will run well around the 250/270bhp mark, and costs peanuts to run

Spend the money putting a proper ecu on, or find a full efi set up and run a ofam ecu if you can find one, it’s boost monkeys plug and play version of a ofab ecu but with mega squirt internals etc