Sorry Fekbmax, both would work but I would rather find a 4.233-4.250 block, than spend $6000.00(w/shipping) on a block that I would have to bore and hone to 4.250 or so and then be limited by the 4.280 max bore.
The 4.300 block would only allow for .013 or so of rehone/mishaps, to maintain the .080 overbore allowance by NHRA. 4.233 std bore + .080= 4.313 Both would work of course, but I would rather find a block that did not require added expense/labor.
I hope you understand.
RJ