OK. I missed it. The 250/327 was not available in the Chevy II.
In 1965, the Chevy II was available with the 300/327. IIRC, it had dual exhausts. 66 model IIs had a 350/327 option. In 67, the top option was a 275/327. FWIW, the II didn't join the big block party until 1968 (350/396 & 375/396). Yenko built less than 40 427CID "Super Nova"s. But I digress.