Small Block Mech Fuel Pumps?

The M6903 should be good.
'Should be' because companies change stuff and we only find out the hard way.
The Holley '110' mechanical pump p/n 12-360-11 has been a solid performer for me.

Mechanical Fuel Delivery for Mopar LA Engines

Mopar Performance and Edlebrock had 6 valve pumps which should work fine but only IF installed on an engine with a '69 down water pump.