Pinto water works

[Not Anumber]

Please can a kind soul with access to a Sierra manual tell me where the heater needs to connect into on a pinto lump ? I've got hold of a classic mini heater and a running car but without the Sierra manual I cant work out whether i need to cut the pipe which goes to the the auto choke and put the heater in series with this, whether it should go in the other pipe the same diameter instead or whether to put T pieces into both these existing pipes and connect the heater accross them.?