Complex sentence: The RAF placed an order for 487 Ventura Mark IIs but many of these were diverted to the USAAF, whih placed its own order for 200 Ventura Mark IIA as the B-34 Lexington, later renamed RB-34.
Split into simpler sentences: The RAF placed a further order for 487 Ventura Mark IIs, but many of these were diverted to USAAF service. The USAAF placed its own order for 200 Ventura Mark IIA, which were put into service as the B-34 Lexington, later redesignated RB-34.