Thanks for the advise guys. I've been out of town for the last couple of days, so sorry about the delayed response. I'm going to scour the local junkyards tomorrow, and see what I come up with. There actually is an '88 325i head on eBay right now. Which as far as I know, is a direct bolt-on replacement for the '88 528e head. I'd gain six intake valves and some hp probably with that one!

On a side note: the shop that the car's at (Tidewater Import Auto Repair on Jefferson Ave in NN) is asking $700 in labor to do the head install with new belts all around, T-belt tensioner, cam seals, distributor cap and rotor button, radiator and heater hoses, and a new water pump. Does that seem reasonable? I don't know what their hourly rate is, but most Bimmer work is $50 / hr. So that's 14 hours in labor...? With all of the parts included, it's totalling $1250. And that doesn't include the head itself! Which is why I'm trying to find a good used head for cheap. The shop said they could get a "low mileage" head for $750! I was like, "No, I'll find my own head."