I have a Heil gas fired hot forced air furnace. I am having Sears install a Kenmore 2 ton 13 seer a/c pump and was told that it would perform better and coll/heat more efficiently if i replace the blower motor with avariable speed one. I am pretty handy and doubt it should present too much of an issue or if I have it in time perhaps i can contract the installer to add it to my bill for installing it. Question is can you even replcae a single stage type motor with a variable speed one? Can it handle that? it is a Heil 5000 - any direction would be appreciated.