[nitpick]Full height drives are 3.3" tall. [/nitpick]
Half height is 1.65". 1/3 height was common for a long time and is 1.1".
I too have a full height drive or two around here. The Seagate ST410800. A bunch of these must have been used in servers because they flooded the used market ten or fifteen years ago and many sellers were not careful about mentioning that they were full height 5.25" drives. They do have a 9GB capacity, which, when they were new, was astronomical and at only $500 / GB they were quite the bargain at the time. The next most competitive drive was still $1000 / GB.
When working, it sounds a bit like a washing machine.
As to the OP's issue, as others have stated, 5.25" to 3.5" adapters were common as dirt back when. There was all manner of sleds and rails which would do the job. The trick is finding some still in existence.
3.5" to 2.5" adapters are still easy. You can pick up an IDE 3.5" to 2.5" adapter kit, through away the little IDE circuit board, and keep the rails.