hey man,
i understand what u mean by budget. I think they are just misunderstanding what you are saying and assuming you're on a 'tight' budget. Which is totally different to shopping around for the best price (I see alot of people on SAU, getting pinged for being cheap, when simply doing thier h/w on prices.)
Also i couldnt see anywhere in your post about you mentioning you were chasing 300-350rwkw? unless you mentioned that in another topic, i must just be blind.
Anyway,
I don't know where your located but if your in Adelaide i have a rb25det AWD sump from a stagea you can have for $150, Then you can do as NIZMOID said an get it custom fab'd. Throw me a PM if your keen.
If not, then all the best with finding a suitable product.
Cheers