Thanks for your comments.
Always thought the engine was a little asthmatic, so replaced the original airbox with a twin trumpet inlet airbox. What a difference that has made, revs more easily and quicker up to speed too.
A question for those who have OD boxes.
I have picked up a J type OD unit originally fitted to a Rootes car, appears in good condition so thinking of a winter project to refurb and fit to the van. Should it fit directly onto the back end of the gearbox? I've seen that the rear gearbox mount needs to be changed and the prop needs to be shortened, anything else to consider?