Yes. To get back to your question, 305 heads will work on a 283, and the combustion chamber size is very close too.
I had a set of old Corvette dual-quad 283 heads that I recently gave away. I wish I new earlier, I'd have let you have them.
The 305 heads have bosses drilled and tapped for accessories that the 283 heads lack. Other than that, very similar.
BTW, I wouldn't suggest 70cc heads on a 283 unless you need really low compression for forced induction. 305 heads were 58 cc's and 283 heads were slight less than that, if I remember.
