brick,
#1-sounds like a great candidate to put a 383 stroker assembly in. Check the PAW catalog. http://www.pawinc.com/

#2-sounds like they might be Vortec heads. The holes you described were modified because the bolts go in at a more vertical angle.

#3-from '86 on the SBC's had the "center bolt" covers. There are lots of aftermarket, and a couple factory covers that look better. However, they do clamp better for sealing than the older style. But, if you really dislike them, adaptor plates are available to allow the use of the older style covers, they run about $100.