This is the best I could come up with. When 2 PK numbers are offered, i would suggest maybe going with the small of the 2 numbers. I will order a 6PK1800 for my car and give this theory a shot.
900 model 94-98
49 04 728 aka 6PK2635
Short Belt (bypass middle idler)
49 61 066 aka 6PK2455...