IMO it depends on how much you are getting them for. Under $1000 I'd say go for it
They are a little too large for a 302, but will still be better than the GT40's you have, and will be nice if you ever decide on a stroker or a blower (or both
)
You're headers should be fine as well. Which ones do you have?
I think Ultraflo is being awful conservative in the ET guess he gave ya. I'd guess with a bigger mass air sensor and injectors, that you could cut atleast 4 tenths from your previous best, taking into account comparable weather and traction
good luck,
-drew