I have several engine stands and would like to instrall geared heads on them but am haveing no luck finding replacement heads or parts to do this, Any Ideas??
R/T

Surplus Places -- or junk yards. Look for worm drives (with a worm
drive, the motor can not slip back).

Some right angle motor drives will have worm gears, but other times
just straight bevel.

https://www.surpluscenter.com/item.asp?UID=2009111012025163&item=5-1663&catname=
(Add a big sprocket around the center of the engine stand, smaller sprocket on the right angle drive... chain around 'em)

Brings up the question.... why? If you are building a big diesel, then I can see the motor drive to assist in flipping it over as you build the crank, then add on the head. For most engines, just a flat plate with 8 notches in it will keep it from rotating (but you have to muscle is around).

https://www.surpluscenter.com/pages/132.pdf

Two motors shown lower right are the worm drive style that you should use.
$89 or $149

weld a old flex plate on the back and place to bolt a starter and make it electric drive. auto locking hub might work for the lock.

weld a old flex plate on the back and place to bolt a starter and make it electric drive. auto locking hub might work for the lock.

yea, if you want to spin your motor an entire revolution in 1 second.