Someone here may know the answer, but if not, the LH car part number is 4792184AD (earlier years), superseded to 5017188AA. LX LIM P/N is 4663850.
From the photos on ebay (http://www.ebay.com/sch/i.html?_odkw...LX%29&_sacat=0), they look very similar. Unless you can prove to them that the essential details they will be working in are identical, they likely won't want to take the risk, especially since it looks like they work on a core system.
'98 LXi - Later Concorde gages (black w/ chrome rings)/'99 LX - LHS gages (white) - HIR bulbs
Honestly, for almost $300 bucks you can do alot more. I realize on the simple 3.3 taking the lower intake off is much easier but I Gasket-matched my upper and lower intake with about 10 hours worth of work overall (this is spread over several weeks.
On the 3.5 LM there is a significant amount of material to remove any the alloy is quite hard. When I ported mine the aluminum came off in extremely sharp splinters that went everywhere. And because I got impaitient and started before the porting kit arrived I ended up with gouges in the runners that I had to polish out by hand.