300 power flow for NON C or X decks
7 Bushel Hopper Assembly part # BM20456 Price at MSRP: $399.00
Blower Assembly for 54 In. Mower part # BM19090 Price at MSRP: $473.00
Blower Assembly for 48 In. Mower part # BM19089 Price at MSRP: $473.00
Power Flow Chute for 48 and 54inch Non C decks Part # BM20988 Price at MSRP: $66.00
48C/48X High-Performance Blower BM22696 Price at MSRP $499.00
"Note: When used on SST, LX, GT, or GX tractors, also order one M147451 shield mounting wireform and one AM131219 front mounting bracket."
54C/54X High-Performance Blower part # BM22697 price at MSRP $499.00
"Note: When used on SST, LX, GT, or GX tractors, also order one M147451 shield mounting wireform and one AM131219 front mounting bracket."
The Dealer would be correct if you had a GX 345 with a C deck but since you have a regular 54inch deck you would need one of the top two powerflow assemblies for the 345's 48 or 54inch deck.
Hope this helps :thThumbsU