The body screws are very likely #6-32 size by about 1/2" long. Thats what K-Line used for most body mount screws that I have delt with.
Also the smoke unit body screws may be #4-40 but I wouldn't want to guarantee that. I have never worked on one of those smoke units.
If you take the body shell and the smoke unit to your local Ace hardware, Lowes, Home Depot whatever, you should be able to match up the sizes and then you will at least know what sizes you need.
Rod