Originally Posted by robert@rittenhouse
No, the D403 regulator (part # 9910-GR40) is slightly different than the D30 regulator (part# 9910-GS40GI) and will not easily fit onto the D403. I think the bolt holes line up, but I seem to remember that the bottom of the GS40 overlaps with the head of the pump.
So unfortunately the 9910-GS40GI is needed to switch over your sprayer.
Being a cheap bugger, is it possible for me to construct an adapter to make it fit?