Stock 318 Roller Conversion

I'm currently using stock 318 72 heads that have been bored to 1.88 intake, 1.60 exhaust, and milled a little. The lifters are hydraulic and my cam is a Mopar Purple Shaft for the 340. Is there any way I can replace my rocker arms with a roller rocker set off of Magnum heads? What length pushrod do I need? Thanks for the help.