You can use a studs or wood nailer strip to reduce the amount of sqft you'lll be losing on the block.

Get some real prefinished hardwood for $2/sqft, buy a chopsaw and rent a nailer for $50. 

. --------------------------------------------------------------------------2nd question:3 of the 4 units have very dirty coils and ducts.

For all he knew, the fuel line had burst or the coil failed, and oil or water was filling his basement.  

Just for a condenser and coil, single system? 

Copper coil ripped apart from walls and even ceiling.

Often very dirty) for lingering cigarette after paint (Some odors may stick to the grime on coils until the condensate washes the coils. during ac season. ) Put vinegar and a lttle baking soda in all ptraps maybe.

I just had both A-Coils for HVAC pulled out within the last 6 months..cleaned and recharged..no leaks were present per my HVAC guy and Condensers serviced.

I will get the coil stock from Job X, a couple packs of light bulbs, bring my DeWalt kit, and stop at the plumbing supply house.

A palm nailer and an impact driver have proven to be very useful new additions.