It may be worth your time, since your car is carbureted to go and get it dyno tuned. The jetting of the carburetor can effect power alot as well as initial and total timing. I'm no expert about times, but unless you spun like crazy your time seems a little high. What altitude are you racing at?
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Mustang Parts Specialties ripped me off, it could happen to you as well.
'84 Mustang 5.0 LX
my LX
'89 Mustang GT
my GT