What to do with a really bad fit.

What would have been the correct way to fix this problem.?

I have had this Revell Ford F150 stepside for quite some time. It’s been slowly assembled and set aside numerous times. I am finally back at it and have gotten to the Dash and found that it is in 2 parts!
The area where the Gauge are (includes a “pronounced overhang”) is separate.

The fit is horrible. I tried several times to dry fit it and then glue it but each time I would be left with gaps or the thing would not hold together (using CA glue medium set “speed”)

Finally, I used masking tape to position it as best I could and then putting beads of superglue on the back side. It holds and it looks ok, but I know that it is poorly fitted.

Use plastic card as shims, sand so it will fit with no gaps and then glue together. Plastic card works great when there are big gaps.

berny’s right. Use some plastic sheet as a shim and if there is a serious gap that can’t be corrected by CA, a few touches of filler putty (squadron green is the best I’ve used yet) should do the trick.