Alan
I think you will have to switch to a early style front motor cover and a standard rotation water pump to get this to work. The exploreer front cover is shorter than the early ones.
Here is the part you mentioned on Marches website
http://www.marchperf.com/pg30.html
Read this warning
1965 - 1969 289-302 C.I. Alternator and P/S Brackets
Requires passenger side lower radiator hose.
Part #30351 - Alternator Bracket: Billit aluminum, Clear powdercoated and stainless steel adjusting rod.
It looks like you could get a early front cover and a early water pump and you will be able to use this part.