Resp:
Yes, that is true, but that was sometime after the French and British ordered the Lightning. Not sure if the British just went along with the French insisting non-counter rotating Allisons. The French and British were listed in the same sentence describing the engine change. Not sure if they both insisted, or that the British just went along with the idea. The reasoning was that they already had or were getting Allison engined P-40s (Tomahawks?).
Yeah, this lines up with wot's said in the books. According to Air Arsenal North America Aircraft For The Allies 1938 - 1945 Purchases and Lend Lease by Butler and Hagedorn (Midland, 2004):
"The Lockheed 322 (P-38) was ordered in two versions, the first 143 aircraft with the mechanically supercharged V-1710-C15 engines to provide commonality with the powerplant of the Bell Airacobra and Curtiss Hawk 81A, and the balance with V-1710-F5 engines having single-stage turbosuperchargers...
"The main reason for the use of mechanically supercharged engines was the limited production capacity for turbosuperchargers, which had been reserved for USAAC orders."
Initial allocations as written on paper were 250 British and 417 French Lightnings. The British order was initially placed with the British Purchasing Commission directly for the RAF, but the French set up their own version of this and both combined their requests under the joint organisation. Only three of the aircraft ordered got to the UK from this initial order and only one was evaluated by the A&AEE - Lightning Mk.I AF106. Their view was that the aircraft was pleasant enough to fly, but its performance was restricted to 300mph and it had no armament and trials involved only a brief assessment of its performance:
"Handling was pleasant, although the elevator was heavy, the stall at 78mph (flaps and undercarriage down) straightforward, and flying on one engine comfortable and without foot loads down to 115mph. The red and green colouring of the engine controls was praised as was the tricycle undercarriage."
The examination of the aircraft was purely out of interest as the RAF had already rejected the Lightning Mk.I on the basis of its poor high altitude and speed characteristics, discovered by RAF pilots over in the USA. This is contrary to what is often claimed, in that the aircraft was rejected based on its A&AEE reports, but by the time AF106 got to Boscombe Down in April 1942, the RAF had already made a decision on the type.