Thanks for the quick response!
Here's a picture. It looks like the anchors / holes are already there for the FD4 in the front.
View attachment 3329788
My apologies for the dusty, dirty bass. I can only blame the lighting.. ;-)
Your pickup looks to be the same size as mine so you'll have to email Dingwall and see if they can provide you one that will match what you have. Mine is a Super Fatty not an FD4 (note the SF - 5 on the underside) take your J pickup out and look at the label it will tell you what it is.
I know for sure that they won't have an old Super J5 pickguard so you'll have to have one custom made or get very lucky finding a used one, they are around though.