Nice project car. As you said, they were fairly advanced technology back in the day. They didn't sell well, though. The 4WD & steering added a lot to the weight and the cars couldn't compete on the track. Compared to the Optima series at the time, the Progress & Gallop were clunky; the Optima series were so successful because of their sleek, lightweight design.
That said, the Gallop/Progress handled very well, very good turning...almost TOO good, in fact. They just seemed to lack that fun factor that you get spitting out rooster tails of dirt at the beach; they'd just turn and move along. I remember watching the Kyosho promo video for the Gallop/Progress and it turned great...but you'd be hard-pressed to get it to fish-tail with a stock 540 motor, and that's half the fun.
They're great-looking cars when restored nicely.