what smallblock (with freedoms)

theres a class running in australia atm i'm considering having a play with,

there is no minimum weight for vehicles pre 1986, where any car after, with a 4 to 6 litre engine has to be over 1455kg, (think i can get under 1200)

the block must be a production block from the same manufacturer up to 6 litres, which allows;

225,
215,
245,
265,
273,
318,
340,
360,
5.7 hemi
and the 6.1 hemi might just scrape in as it's only marginal cc

forced induction is allowed, but is calculated in a way that only the 215 hemi can be used, and a restrictor plate of 36mm must be fitted to the intake for a single turbo or 27mm for a twin system

INTERNALS ARE FREE!!!

what would you use as a starting point? I'm thinking between 340 and 360?