If you are getting the old style Chamberlain safety sensors with the round LEDs, they should wire-in exactly like your existing ones (i.e, twist white wires together, twist red stripe wires together and insert in respective terminals on the GDO unit).
Old style sensors
View attachment 196792
New style sensors
View attachment 196796
If you are getting the new style sensors with the rectangular LED lens, the Chamberlain wiring instructions will likely be incorrect for your older GDO. I could not get both sensors to light up by connecting white to white and red stripe to red stripe. I finally got them to work by twisting a white wire with a red stripe wire and then connecting each mixed pair to the GDO terminals. Also, there was a bit of trial and error since the new style sensors are polarized. If both LEDs don't illuminate on your first try, just flip the mixed paired wire connections at the GDO terminals until both LEDs illuminate.