Just find yourself a Junked F 150 v6 and buy the whole long block. You can stay single port, its been done already, but if you go dual port it will get you more hp. If you want single port, use your present heads and intakes and everything else from the F 150. You want to get this from one with low miles and a good engine, if you do that the only thing you should need will be gasket sets.
Might as well get a set of ARP head studs, you can't reuse the stock headbolts at all.
The only reason for changing the pistons, and or rods, etc would be if you plan to supercharge or turbocharge this engine, then you would need forged pistons and rods, otherwise use the stock ones and a good new set of rings and bearings.
Rick Kilpatrick, AAS Automotive Systems Tech, Alamance Community College, Class of 99. 06 5 speed manual Mustang with Pony pkg : GT Mac Mufflers, true duals with one custom pipe. 2.5" system. GT bumper cover, all installed March 7&8 2006. AFE Stage 1 CAI, Motoblue Underdrive pulley, GT aluminum shifter knob, honeycomb rear blackout panel,and dash kit installed. Roush hood scoop and side window louvers installed. SS taillight trim has been installed, new alum. GT steering wheel installed.