I have a 1972 ford mustang 351c I replaced the water pump only used one gasket did I need to use both of them I got it running today and water is coming out of the left side of the motor by the oil stick did I do something wrong.
if the 351 is similar to the 302 as far as the pump... the bolts on the left (pass) go into the water jacket. u need some kind of sealant on them. if it really is leaking from gasket u gotta pull it and see whats going on. on side note when getting gasket kits a lot of them come with duel gaskets... some fit and the other will not. this is true if u get a rebuild gasket kit...
If you have a leak there is something wrong for sure. Are you sure hoses are in place and tight also?
When you had the pump off you should clean all the bolts really good and I apply some anti seize and bit of RTV to the threads of the ones that go into water jacket. Cannot say by memory which ones do.
You should apply a small amount of RTV or sealer to both sides of the gasket. It is also easy to knock the gasket out of position when installing. It is a great help to take a couple of long bolts and cut the heads off and put one on each side to slide the gasket over and get in place then slide the pump on and get the bolts started and then remove your guide bolts. You can also use threaded rod cut to length.
You also need the special thermostat for a 351 C or you will have heat issues. Correct one is shown in the picture. Has a hat like extension that goes into the baffle down inside the block. Use anti seize on the thermostat housing bolts also.
and the timing covers get pitted over the years and if they aren't in good shape, a seal can be hard to get without a good sealant added to the gasket surface.
Probably have to pull it and try again, but the second time will be easier.