The OP's part number is for soft (170# springs) the number you provided is for firm (300# springs). I can't help as to which is a better setup, but I was curious myself and thought I'd pass the info along.
Did you end up pulling the trigger on the Boss wheels? If so how did they work out for you? Pictures/details would be a welcome addition to the official wheel/tire thread.
Guys I'm posting this for my neighbor who had a very nice 1986 black T-Type stolen from his car lot in Saginaw MI this weekend. It was taken from American Auto Group located near the corner of Bay and Shattuck Roads sometime after 10PM Sunday night. It is a black car, chrome bumpers, gray...
I'd say If you can afford to pay cash for it go for it. If its as nice as you say then at that price you really can't lose. If you end up regretting it you can just sell it to me. ;)