My 87 Bonneville currently has 14x6 steel wheels. I want to upgrade to the diamond spoke/crosslace rims.

I could get 14x6 diamond spokes and I know I wouldn't have to worry about the fit at all, but as long as I'm upgrading, I'm thinking about going up to the 16x7 diamond spokes that were on some of the 94 - 99 Bonneville'*.

The lug pattern is the same 5x115 for both wheels, but I'm unsure how much the 1" difference in rim width will affect the fit, if at all. I know that in order to not mess up the speedo, I'd have to get tires with a smaller aspect ration,and that as the aspect ration gets smaller, ride quality tends to decrease, but any other thoughts on side effects that jumping from 14x6 to 16x7 would have are appreciated.

I think you have it all right. Personally I would go with the 15 inch tires, stay normal profile and enjoy the better ride and handling. You'll get used to the small speedo difference.

The problem with the 15'* is that they are hard to find. I found a set of 14'* online, and I've found 16'* online. I want the stock look of diamond spokes, but I feel like the 16'* would still look stock, but would look a little nicer, and in case I ever need to replace one, I think they'd be easier to find.

I don't think ride quality will be that big of a concern, I just wanted to make sure that I wasn't overlooking some obvious problem that would crop up when switching from 14x6 to a 16x7. I won't be buying them until this weekend at the earliest, so if anyone sees a flaw in my plan (buying 16x7 rims and putting 215/60-16 tires on them in place of the 205/75-14 tires currently on the 14x6 steel rims), I'd appreciate a heads up.

If no one sees any flaws, aside from some slight reduced ride quality, I'll post pictures once I get the new tires put on the car.