I'm posting how I did the rear main side seals. I have engine in the car. Cannot fill the side seals from the outside of the block so this is how I did it.
Equipment:
a) Mancini retainer with the o-ring side seals. DID NOT USE THE ORINGS. My OEM retainer was damaged. Oil pan screws poked thru due to using wrong screws.
b)5ml syringe - 14ga blunt tip needle 4" long and 1.5" long. Amazon.
c)Permatex ultra grey. I dont know if there is better RTV. I checked clear RTV and utra grey, and grey seemed tiny bit thinner. Need to be able to get it thru the 4" needle.I did shorten the 4" needle about an inch.
d) Made a handle for syringe from a house light fixture attachment bracket.
e) permatex 518 - for gluing the main seal ends.

1/17/18 Update: Thinking about this after doing this, I found 3mm needle on amazon. Look up "sauce injection syringe". That would flow the silicone much easier. I would still hook the needle to 5ml syringe.