I got some classic Epic whirlwinds off ebay recently. I have decided to divide my Space Marine force into Pre Heresy and 40K style components so these go with the Pre Heresy side.
Metal versions of old Rhino chassis with a very square launcher.
Launcher is pretty sizable compared to the tank body.
Back view shows the missile exhaust vents.
Here is the scale of the launcher. While the old rhino chasis are pretty common these rectangular whirlwinds are not. It you want to make a scratch built one they are about 9/32 long, 7/32 high, and 8/32 deep so you could probably make it out of a 1/4 inch plastic rod as the base with maybe 10/32 length. Then just drill in the hole pattern. The missile ports are like 1/16 in diameter with 3/32 spacing between the two rows.