Quite a common thing in the 40s and 50s to see various engines installed on 4 engine test beds - after all, they generally had the best performance to cope with the extra weight.
Here's an interesting one (the single engine B-17's a photoshop job of the 5-engine photo!):
B-17 test bedsAvro Lancaster's tended to be a bit more interesting! As test-beds, they had engines in place of the outboards (jets and props), nos mounted props, bomb bay mounted jets and tail mounted jets! Quite a selection!
Lancaster Test Beds