Getting Lean and Fast,
I think you're on the right track, but don't get obsessed with the weight-loss, or see it as the only route to getting faster.
My story is similar to yours...
I ran fresh/soph cross-country in HS (16:30 5k @150lbs) before quitting to focus on off-season strength training for basketball. Didn't get back into running till grad school, and by that time I was 190lbs from lifting and working construction (I'm 6 ft. tall). I completely replaced weights with running, and lost 20lbs almost immediately. I raced a 10k and beat my HS 5k PR in the first half (serious positive split). At that point, I was completely hooked on running and began to think, "man, if I can run 34mins @ 170lbs, imagine what I can do @ 150lbs." I continued to train and improve till I reached 160lbs, then, something amazing happened... I started getting slower!
160lbs was the magic number, and as soon as I dipped below that, I started feeling weak. If I gained a couple lbs, I would feel good again. I continue to experiment, but I am close to accepting that 160lbs is my racing weight, and future improvements will have to come through strength.
My advice: don't worry about getting down to 148lbs. Just keep fueling properly and training hard. Set performance goals, not weight goals. You may find that you are faster at 155lbs than 148lbs.