try seaway. if you have the part ##### ask your dealer if he does not have them ask him to look on the NOS site and see if another dealer has them . I have had good luck with this method. also try Joe Poole.
I was able to get new upper and lower mounts for my '60 800 from Joe Poole. The bolts for the mounts, another story. Milled off the bolt heads, popped off the broken mount covers, drilled out the remainder of the bolts on the lower mounts, and drilled out the bolts on the upper mounts. I was able to bolt the midsection on the table of a vertical mill so the bolts could be drilled out with some reasonable accuracy. A very PITA task.
Joe I got your email and I may be coming to you for the mounts. So far the mounts that I've removed are all in good condition.
Despite my best efforts the bolts holding the bottom covers sheered except one. I will follow your advise Larry as I know someone with a mill who can drill them out for me. Luckily it was one of the blind bolts that came out so that we know how long they are and will know how deep to drill. The top mounts are proving equally difficult to get out and I've had to drill the heads off a couple of the screws. There's one more top mount to come out. There was some corrosion on the heads of the bottom bolts.
I've started work on the lower unit but I'm having similar problems as the lower pump housing is held fast by the close tolerance of the studs and the gasket sealant. The sealant is similar to a product that used to be available in the UK call 'Red Hermatite' I don't know if this is original or if it's been applied later.