Talk to Fredness, he's the 3.0 V6 guru he'll have any info that you made need.
Rogue Roller lifters and performance tuning will be what I would recomend. I haven't used them yet but from what I hear and have exp. on someone elses ranger it the best thing you can do. Also you may want to add a K&N O.E.M direct replacement air filter and change to 10W30 motor oil. Also change your exhaust but keep the stock size pipe. This will give you an 18 to 24 MPG's over the stock 14 and 17 Mpg's. Changing the roller lifters with the heads out will be even easier considering that you're changing the heads to begin with because rogue roller lifters the heads stay in the truck when you install them. Here's a link where you can get them: www.rogueperformance.com
. They carry the roller lifters I mention plus a whole host of other mods and parts you would like.