Actually, if your 89 has the factory motor, it has a roller cam, it's just not the same firing order as the HO. You could use a GT40 long block, but you really would need to change your intake and exhaust to get the power you want. The difference between the non HO and HO motors is:
Throttle Body
EGR spacer (diameter)
upper intake
injectors
heads
cam
headers
That's about it. And you need a new computer. So, you'd probably be better off getting all of those parts off of a Mustang for pretty cheap (I got mine for my Cougar all for about $400) and bolt all that on and be running at 225HP pretty easy. If you want some more info on this check out
www.coolcats.net Go to the tech section and find HO conversion. Like I said, I've done this conversion on my 88 cougar and it was not very difficult, took about a weekend. Have fun, if you have any questions, email or post. Good luck.
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Michael Black
Quantum Motorsports
Norman, Oklahoma
1988 Merc Cougar 5.0 HO, P&Ped heads, 2.25" custom mandrel bent dual pipes, T5 five speed tranny
15.43 @ 91.08mph (not shabby for a 3600 pound car)
60' 2.453 Street tires suck!!!