Upgrade 2.25 to 2.5, what do I need?

I got a 2.5L petrol motor from a friend in excellent condition to replace my tired 2.25 in a Series 2. Does anyone know what i need to finish it off? I want to keep my Series gearbox though I do have the LT77 that came with the 2.5 from 1985 Defender. I assume I can use my 2.25 flywheel and clutch (though I will replace the disc at a minimum) so I can use the Series throw out bearing. I also think I can use the thermostat housing so I can use my Series radiator since the Defender radiator has a different hose position. I know I need to switch to an electric fuel pump as the 2.5 doesn't have a spot for a mechanical pump.

Are there other things I am not thinking about? I want to have everything as ready as possible to do the engine swap. The wisdom of the forum would be appreciated.

I have a similar issue, hopefully some answers will be forthcomming, otherwise we'll have to learn new dog tricks.

I am not 100% sure but I believe you need to keep the 2.5 flywheel and fit a 2.25 9.5 inch Diaphragm spring, series 2A clutch complete, that will match up with the release bearing in the S2 gearbox . If you have the twin choke carb. on the 2.5 it will need a recirculatory fuel system with a feed back to the tank , similar to the diesel. I fitted a Diesel 2.5 in place of a 2.25 and did as you suggest fitted the 2.25 thermostat housing to keep the Series radiator. This also enabled the heater on/off valve off the Series to be used , as the Defender uses an air blend heater with coolant circulating through it all the time.

Thanks for the info. I was thinking the same on the clutch. The Weber carb is a 32/34 DMTL which I don't think has a fuel return, but I will have to get an electric fuel pump. This carb has an electric choke and anti run-on valve which I assume just connect to a positive, keyed lead like the coil. If anyone can think I what I am missing I would appreciate it. I bought the engine for the upgrade and to make it a swap so I am not down for long. I am also going to get the head milled to go from 8:1 to 9:1.