Replacing leaf springs and maintaining OEM ride height

I've baffled the online 'experts' by asking if a particular set of
leaf springs will maintain the OEM ride height of my 97 Tacoma 4WD.
I was particularly interested in a set of Pro Comp springs (price is a
factor at only $110 a pop)
They are advertised as having a height of 3.5", but when I questioned
customer service as to whether this was the same as stock, they
couldn't answer.
It's a 4-leaf set, so I'm thinking it can't be much different than
stock, but I don't want a jacked up rear end if I get these things (I'm
currently a leaf short due to hauling too much firewood)

Anyone have some insight as to what to expect/look for in aftermarket
springs?
I don't want to "trick my truck" - just give it some extra carrying
capacity.