Nope ! My R/B water pump catalog shows 59 to 62 the same. Rebuilding is not hard if you have a press and a puller or 2. Bigger prob is getting the parts ,aftermarket W/P kits went out of fashion 40-50 years ago.
Yeah the 1963 water pump is different from a 59-62 water pump. A 1963 still has the 390 engine but it is different from 59-62. Remember there are two different kinds when ordering a waterpump with A/C and without A/C. I got mine from Kanter but paid a ****load plus charged for the core price. I've seen them on ebay a couple of times.
E-mail this guy. chipscaddys@yahoo.com He's from Troy, MI. He had one for my 57' 365 Caddy which is the only year for the lower outlet on the p***enger side. I'm pretty confident he could help you out and he is a hell of a nice guy with a price alot better than Kanters. Or you can ask a good parts store the address to a H2O rebuilder and send it off seeing that part stores don't have a part # listed.
I looked into this a short while back for a customers '59 390 & Kanter in NJ came up cheapest by far! Kev.
Had this guy rebuild mine for $150 plus shipping. He installs impellers with more vanes and puts fresh bearings, seal, etc in it. Two week turnaround, just as he promised. http://www.howardstewartrestorations.com/index.html Gary
I found a place on the internet called Falcon Sales e-store and they advertise a 'new' water pump for a 1960 Caddy for $167. "1958-62 caddy 365 390 V-8 with or without AC. Brand new pump with improved seal, leak tested, complete with gaskets, and new br*** fittings, ready to install." Anyone dealt with them before? (Kanter was $208)