DTS OEM radio in a 95 Fleetwood???

as a direct bolt in? no. it looks too wide, and its not square, so you have to modify either it or the dash. you'd also need the harness for it , theftlock code (if GM still does that), plus you have to bypass the fleetwoods external amp/ tuner box. some GM radios even require the cars radio to link into the BCM/PCM.

I've heard of guys putting radios from higher end buicks circa 2000 in their fwb's. they look factoy (because they are), have CD and tape, and IIRC a 200 watt amp. you could always mod the radio to put an 1/8 inch jack into the outputs from the tape mechanism to the radio itself. I know it can be done on the 1.5 DIN radios as well as the old 2 post style, so I don't see why you can't do it on the newer radios. no dremel required, just a solder gun.
btw, you shouldn't need a $50 wire to bypass the tuner box. run new speaker lines, new ignition and constant power lines, and a ground to the new radio. its not hard, just time consuming. leave the tuner box as is in the trunk with power.

that harness is not for that radio. note the offset split in the harness plug, whereas the radio has a straight split. that harness is for a GM radio from the late 90's.
the databus will input into the radio through the harness. sometimes the databus (or ECM/PCM) communicate to the radio (sends it a signal that allows the radio to work- no signal=no radio), and sometimes they just provide power to the radio. If the radio receives a signal from the databus (and not just power), it will be a major ordeal to install (and costly) since you will have to install the computer from whatever car the radio came from in order for the radio to work, and even then it might not work.
How old is the radio you want to install?

I really have no idea what kind of signal some of the databus send. I just know that some won't work without the computer (since everything ties in together on the newer caddies.) the bose HU (from a 91 seville) in my caddy hooked into the BCM/PCM data line, but it was actually just the constant power and IIRC dash lights.