m20 or m21? (or something else) HELP

[vasrox]

Im trying to identify this gearbox. The numbers are:

HOLDEN 3 7433771
It has MR on the cast and 305 stamped on the rear alloy case.
And it doesnt have any groves on the spline (shaft).

Any help would be grate.

HOLDEN 253 , 308 VB,VC,VH,VK 4 SPEED GEARBOX m20 or m21 - eBay VB, VC, VH, VK, VL, Holden, Car Parts, Cars, Bikes Boats. (end time 04-Oct-07 20:34:34 AEST)