Lifting that kit is easy. Just scale it out in inches, and then get the appropriate thickness of sheet plastic.
Scale Auto actually had a small tut in light commercial on these very kits back in the day, but I don't remember the issue. Anyway it goes something like this.
After finding the scale thickness of sheet you need, use a pin vice and drill bit of the right diameter and drill all the way through the mounting holes for the suspension. Then cut and sand to shape the sheet plastic to the right dimensions needed, and glue into place over the mounting holes. After a day or two of drytime for the glue(your judgement), use the same drill bit and drill from the backside. You now have a lift, you can use stock suspension pieces, and the suspension parts will fit perfectly, because the holes are in the exact location and the exact same size as the original molded in mounting holes.
Now if my description is a bit confusing, let me know, and I'll grab a scrap kit around here, and add a quick lift to part of it. Unless you are looking for a BIG lift, in which case......... the best way to go might be working suspension, as it's only a couple of added simple steps and an omission of a couple of steps to make it working leaf spring suspension.