Kym's 13B makes over 350rwkw, he gives it no love at all. been going strong for years.
To be honest knackers there is no Perfect solution here. Just go with whatever you are keen on
and stick with it. Any Stock road car engine is not going to like track work. It is a matter of time
before it pops.
I would say spend the 8 on the RB25 you have. good rods and pistons, bit of head work and springs.
That will make it reliable and get you over 300.