I have a 89 full size 5.7 I live in the pocono's where it's very cold some mornings. I purchased
a Kats external tank heater, and wondering if anyone has installed one, and can give me a bit
more on installation tips.

I really do not want to cut the lower radiator hose, or put in a plug in the block. (especially this time of year)

Can I cut the hose coming from the intake manifold to the heater core and install it there?

 

Doesn't it come with installation instructions? I just had a look at it and it appears to have the heater hose size connections.
I'd say yes it should work in the intake side.

 

Yes, it has instructions, and they are not great. Bascially they tell you to hook it up to the lower radiator hose,
or to the block.