I put relatively low cost air conditioning (< $2K) in my L-IV P using the stock TSIO 550 E1B engine sometime ago and it seems to work pretty good.   I would not recommend my unit for a retrofit but it was a pretty easy install before the fuselage top went on.

The key to my installation is using the TCM compressor bracket that mounts on the rear of the engine.  See page 09-05 in the engine parts manual.  This is the one expensive item.  TCM  asked $ 1400 but Lancair ordered it for me for $ 700.  Also, there is room to mount a backup alternator on the accessory case, but I had to move the battery from the firewall  to the  baggage compartment to make things fit.

I use a small Sanden A/C compressor with bulkhead fittings to route the freon hoses (#8 for pressure and # 10 for suction) thru the firewall and pressure bulkhead to the evaporator that is mounted in the rear of the fuselage under the inlet for the overhead airduct.  The cold air from the evaporator  is sent through the overhead duct into the  cabin using the six eyeball vents in the console for distribution. I left the 3 inch blower in the system to provide additional circulation when needed.

The only real compromise in this system is in the size of the condenser that dumps the heat from the freon as it expands. Here, larger is better but where to install???  I found a thin unit measuring 12x18x1inch and mounted it under the baggage floor where it just clears the gear legs when retracted  To increase efficiency, I routed external air thru the condenser from the NACA vent in the tail, using a 4 inch blower to cool the condenser.

My system is designed to provide A/C  only on the ground with the engine running .  I use an "either-or" control switch that selects Pressurization or Off or Air-Condition

Additional details available on request.

Regards, Bill Hogarty