440 Engine Rebuild advice

Rowan,
Just some comments.
[1] 020 oversize might refer to rod &/or main brgs. Doubtful it refers to piston size because 020 is an unusual oversize [except possibly for factory pistons].
[2] Streetable, with the HP substantially greater HP than the engine size is often mutually exclusive. It will depend on your definition of streetable & the skills of the engine builder.
[3] Above suggestions of a stroker are excellent, & a better way to go; you end up with a better behaving engine & still getting the desired hp.