Sorry for coming back to the party late, but how did you get on?
The water in the vee will be the thermostat housing. Cheap enough, and easy to fix but... getting to it is a bit of a bastard. You have to remove the manifolds, fuel rack, etc. Pain in the arse, but I wouldn't let it put me off an otherwise good 75. Somebody somewhere does metal thermostat housings to replace the plastic ones that split (trawl the 75 forums). From what I've seen, almost all 75s leak into the boot, but the causes are known and once again, it shouldn't put you off an otherwise good one. The fans do crap out too, but I just rebuilt mine (simple enough) rather than paying the exorbitant sums wanted for a replacement. It's usually just brushes and resistors. Suspension knocks are most commonly the lower front bushes, something the 75 does chew out, but they should last 100,000 miles, and they're not hard to replace. Quite cheap to buy, too, unless you get them from Xpart.