Herald overdrive gearbox

[kart649]

Intend to fit an overdrive gearbox (J type) to my herald ('65 12/50) which will have a mk3 spitfire engine fitted. Have found a company who can supply a recon box and the complete recon overdrive unit. Which gearbox do I need? Three rail or single rail? Which donor car do these come from? Better off with a D type? Which propshaft? Any help greatfully received.

[Clive]

3 rail j typrs are VERY rare, only fitted to some late MK4 spitfires. A d type 3 rail (4 synchro from a mkIV, but the 3 syncho earlier ones work fine too) and the propshaft from a non od vitesse. You may need to alter flanges on the prop to suit the box and diff.
You can fit a single rail J type box, but needs a dolly 1300 clutch plate as it has fine splines, and a special propshaft.
Any conversion will need the appropriate monting plate, rubber mount, angle drive, longer speedo cable AND a switch, either gearknob one (tend to be unrelable with wires breaking IME) or the early spit/vitesse column switch. Choices choices......
Clive

[kart649]

Thanks for the help. As you say choices, choices