Rear main seal dowels

I have a simple question for you that know:
Putting a new rear main seal in my F134 with engine in the vehicle. Removed the old one, no problem.
Rolled the new upper half in, no problem.
After two hrs, still could not get the new dowels and cap in.
Did I get dowels that were oversized or what is the trick ? What is the best way to install them, place them in
the block then slide the cap over them or install in the cap-groove and then slide cap and dowel in place ?
Would freezing them help?
I wound up using one new dowel and one of the old ones.