DC8-60 Series: inboard reversers available in flight with gear handle in up position, but restricted to reverse power stop. All 4 engines with gear handle in down position. I think the older series where similar.
Trident: reversers on engines 1 & 3 available in flight – the descent rate was in rather interesting to say the least. Reverse thrust was indeed selected just before touch down (below 50 ft RA).
MP