The Linistepper needs a really good heatsink. A smaller heat sink can work if it has a fan on it.
CPU fans for the Socket A/370 processors seem to fit well, and we now supply one:
416045
Keep in mind that you will need to drill and tap the holes to mount the power transistors and to mount the heatsink to the PCB. We recomend you drill and tap the very common #4-40 size holes and use your own bolts in place of those supplied with the Linistepper.
We also provide a version with the holes drilled and tapped #4-40 with replacement bolts included; ready for you to install.
416047
The bolts provided with the Linistepper are #5-48. A #5-48 is 0.125 outside
(clearance) and 0.1135 "angle" diameter.
Our tap and drill calculator says
that would need a 0.1047025" size tap hole or approx a #37 drill.
http://www.hermanscentral.com/product/qual-tech-548-high-speed-steel-tap-13368.cfm
is the only source I've found for a #5-48 tap.
OCNC used a different CPU fan and drilled and tapped #4-40, then used his own bolts to connect the power transistors.
The fans have 3 wires, typically black, red, and yellow. The yellow is a sense return signal, and not needed here. The black and red (pins 1 and 2) are the power connection, black for ground and red for +12 volts (although anything from 5 to 15 volts will generally work fine). ^