Get an early SB cast iron pump which will have the hose/pump nipple on the DR side to match your DR side radiator nipple (I'm assuming). Keep the same dampener/tcover. You will have the timing marks and the pump nipple both on the same DR side but you can see the marks if you aim the light just right. I have an 83 318 in a 65 dart with a DR side lower rad nipple/early cast iron pump on the 83 tcover/dampener and it's doable. EDIT the early cast iron pump is thinner than the later aluminum one so just get the right depth pulley and or spacers to restore belt alignment.
www.speedwaymotors.com has em and I've used flat washers. The thinner pump body MAY need washers to slightly shorten the bolt length engagement. Mockup & go from there
