1600 lb is 725 kg, not 1000 kg.
From my recent reading of the air war on the Eastern front, the standard bomb load for the Ju-87B/D was either a single 500 kg (1100 lb) bomb, a single 250 kg (550 lb) bomb or one 250 kg bomb and four 50 kg (110 lb) bombs. Also popular were cluster munitions containers on the wing mounts. Less common loads were two 250 kg bombs or four or even eight 50 kg bombs. The Ju-87B was limited to a maximum load of 700 kg (1540 kg), the pre wing extension Ju-87Ds were limited to a maximum of 1100 kg (2440 lb).
Less common load-outs for the later, strengthened Ju-87D included a single 1,000 kg (2,200 lb) bomb, a 1000 kg bombs and two 50 kb bombs, two 500 kg bombs or a single 500 kg bomb and two 250 kg bombs.
The 1000 kg bombs were generally reserved for large static targets, such as bunkers or ships.
If you go by the manual, the later Ju-87D-5 could carry a single PD1400, SC1800 or PD1800 bomb, although I've never read a first hand account of their use. The actual weight of the two larger bombs varied a little due to some changes through the war, but were between about 1740 kg and 1820 kg.
From the second hand reports that I've read on forums and suchlike, there seems to be considerable doubt over whether the 1400-1800 kg bombs were ever used in combat. I've seen opinions that the D-5 would have been required to delete the rear gunner and all his equipment, take out some of the armour protection and remove the forward firing guns to get the larger bombs off the ground.