Does anybody know if the 48 seat fit on sportster 2004? I'm woried about possible interference with the ignition module under the seat...

I dont think it does not 100% but Im pretty sure you can find plenty of low profile solo seats on the web to suit your model ,try HD catalog ,Mustang seats ,lepara seats and Corbin seats ,happy Googleing . (not sure on spelling) (not good at counting either )

I'm with 48, I dont think it will and Lepera make a seat to fit your model that is very close to the 48 seat. Alternatively, try Mustang!