Ju 86abl:

First prototype, bomber configuration. Originally powered by Siemens SAM 9 radials.

Ju 86bal:

Second prototype, transport configuration. Originally powered by Jumo 205C diesels.

Ju 86cb:

Third prototype, bomber configuration. Later powered by Jumo 205C diesels.

Ju 86V4:

Production prototype for commercial Ju 86B.

Ju 86V5:

Production prototype for Ju 86A bomber.

Ju 86A-0:

13 pre-production bombers.

Ju 86B-0:

7 pre-production transports.

Ju 86C-1:

Six Lufthansa transports with Jumo 205C diesels.

Ju 86E-1:

Luftwaffe bombers with BMW 132F radials.

Ju 86E-2:

Uprated version of E-1.

Ju 86G-1:

40 aircraft modified from Ju 86E-2s with round, glazed nose.

Ju 86K-1:

Export version for Sweden & South Africa.

Ju 86K-2:

66 aircraft built for Hungary.

Ju 86K-4:

Built for Sweden (B 3A) with Pegasus III radials.

Ju 86K-5:

Built for Sweden (B 3B) with Pegasus XII radials.

Ju 86K-6:

Export version for Chile and Portugal.

Ju 86K-13:

Swedish built with Pegasus radials.

Ju 86P-1 & P-2:

High Altitude reconnaisance. Converted from Ju 86D.

Ju 86R-1 & R-2:

As P series but with higher aspect wing.

Sources:
Gunston, Bill - The Encyclodepia of the Worlds Combat aircraft, 1976, Chartwell Books, Inc., New York
Brown, Eric, Captain - Wings of the Luftwaffe, 1979, Airlife Publishing Ltd., Shrewsbury
Gunston, Bill & Wood, Tony - Hitler's Luftwaffe, 1977, Salamander Books Ltd., London
Donald, David - The Complete Encyclopedia Of World Aircraft, 1997, Brown Packaging Books Ltd., London
Wikipedia - Junkers Ju 86