I might be wrong but I don't think the stainless ones are available from Alpina anymore so you might have to settle for chrome plated ones. I know that Alpina offered atleast 2 different stainless ones with the difference being the crown and they also offered their own lock for then. I am planning to machine a batch of them and hope to have them for sale in the next several weeks when the schedule in the shop allows.
OPEN ! all the way. In my opinion the closed ones are more fitting to the 90's Alpina lineup, such as the E34s and E32s. but the E28 needs to have open centers to look period correct.
Given my past Alpina experience (Ti, B6, B9), I would have thought for sure that I would have liked the open lugs best, but in your case I really think the green really sings with the closed lug wheels. Could be I have always lusted after Sia's B7 and that's what he has. Anyway steak or lobster, lobster or steak. I like both.
I've always thought the closed/capped looked great on the E34 (like Anita's B10 BiTurbo), but a little wrong for the E28. They look good, but don't blend for me like the open wheels do.
I vote for closed lug, but it's a really close call. I don't think the "period correct" argument should have anything to do with it, and the the closed lug design just looks cleaner to me.
I guess you better keep both sets, Roy, and just bolt on the other set every few times you drive it. You'll never second guess your decision that way.
One day, I hope to be in the position to have to make this type of decision. Right now the kind of decisions I make are more along the lines of: Fix the truck or the BMW or the Honda. I can never do more than 1 at a time.