From what I've heard, it isn't bad... but replacement parts are a BITCH to get($$$$$$). I actually looked at that for a second.
Personally, I'm going to retrofit a 454 TBI onto my 472 caddy engine. It will require NO custom parts aside from the TBI to quadrajet adapter and the prom of the computer(big bonus for on the trail repair... someone might actual be able to help fix a TBI... good luck with the stock caddy stuff).
The list of parts I have figured for is:
- 7477 ECU ~$40
- 1981 Caddy distributor from 368 engine (I paid $30)
- 7.4L TBI unit... aka 2" bore TBI (I've seen them going for $200 used)
- water temp sensor (I paid $30 new)
- oil pressure sensor
- knock sensor
- fuel pump relay
- fuel pump
- map sensor
- TBI mounted stuff(IAC, TPS)
- ESC module
- o2 sensor
- wiring harness (I'm looking at ~$200 for custom making my own)
Basically, I'm going with a complete TBI swap minus the EGR and smog pump related stuff(1970 cady doesn't have either)
Right now, I've got the distributor and water temp sensor. As I find stuff at a good price, I'll buy it. For now, I'm not in any rush since I've got all the carb related stuff ready.
Ebay has "sensor grab bags" that include most of the TBI sensors for around $40-$50. I'm doing all new sensors on mine for peace of mind.
The two "difficult" things with the retro fit are:
1) Custom prom... I am going to buy a prom burner and software so I can toy with mine to get it to work right(under $200)
2) Custom wiring. Since the distributor is at the front of a cady, painless generic TBI harness won't work. In my case, I've got sensors going in COMPLETELY different areas than where the stock Chevy's were. But the wiring isn't too difficult if you played with a TBI harness before

I'd estimate once I get the wiring related stuff I need, it'll take me 4-5 hours to wire it up.
Hope this helps(and exuse the length... I like to ramble:flipoff2: )