LEngine is telling me the E31 has a 42.4 CC chamber, the E88 has a 44.7 CC chamber, the N42/N47 has a 44.6 CC chamber.
Do you have any reason beside thinking that the chamber is larger to swap a head for performance?
I would suggest searching and reading as much as you can on performance cams if you want to go for N/A power.
*edit* You seem new to this, IIRC E31 and E88s were L24 heads, N42s and N47s came on the L28