This is me Stan
Join Date: Feb 2008
Location: King, North Carolina
Well as far as I know, SO 5.0 came with pistons that didn't have valve reliefs; mine didnt, and people I know with em had the same thing.
When swapping to the HO cam, you need to get a Mustang computer also (which is easy), and you'll need to change the firing order to that of the Mustang; they were different between the SO and HO. I also recommend that you grab a 60mm TB and HO upper intake, both of which can be had for dirt cheap.
1988 Thunderbird 5.0L | 240rwhp - 300rwtq
306ci, GT40 intake, 65mm TB, GT40Y heads, T5 swap, 8.8 disc rear w/3.55s, 11" front brakes, MM front & rear control arms, front coil overs, Koni yellows
Retired DD - '88 Tbird Turbo Coupe - 99.9% stock
Current DD - 2015 VW GTI SE 6spd manual