Lockheed Ventura Mk I and Mk II differences

[Larry]

Guys with regard to the RAF Lockheed Ventura Mk I and Mk II what were the differences?

I know that the Mk II had a Pratt & Whitney R-2800-31 Double Wasp, rated at 2,000 hp, which I think was the same as the USN PV-1

I cannot find the P&W Double Wasp engine type for the Mk I.

What other differences were there between Marks, as the defensive armament looks to be the same ?

Lastly, was there an official designation for the Ventura Mk II which had a Bolton-Paul Mk IV four gun turret, fitted in place of the earlier egg shaped BP two gun turret. While I have seen these BP Mk IV turrets in use on the Venturas in the Med, no author has picked up the type or the fact that they were used in the UK, in 2 Group such as this in the attached photo while serving in 464 Sqn, when the Queen (Mother) paid a visit.

Perhaps Mk IIB might have been used?