As FIA have been kind enough to make most old homologation forms public here
http://historicdb.fia.com you can find most '02 goodies described in a lot of detail. Including 4-valve heads and guillotine intakes....
http://historicdb.fia.com/sites/defa...58_group_1.pdf
I suppose today it's all about serviceability and endurance in historic racing but most are pushing over 200hp reliably from a 2-valve carbed M10. I've seen these guys run a few cars like that, and they do it very well!
http://www.engels-rennsport.de/projekte.html Last time I was there they had just started another new build for stock. (yes shameless plug, meet them and you'll understand)