Re: 98 150 4.2
You'll need to do some fabricating as the 5.0L was produced in the previous gen F150. I'm not sure how well it'll bolt up, but you'll have to do some work, to make it work.
If you want a V8, 5.4Ls are quite common now in used vehicles and even at salvage yards. You might need a new bellhousing to mount it up, but you'll also have to beef up the transmission to handle the torque. A 4.6L is also a viable option. Personally, I'd think twice about the 5.0L block, but with enough time, money and patience it can be possible.
'00 Durango R/T 360ci 290hp (modded); 138,500m
'06 Pontiac G6 GT 3.5L 220hp; 44,000m
'12 Chrysler 200 Limited 3.6L 283hp; 13,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!