We bought a recon 2.1 from Remtec a couple of years back now, it was pricey - about £1400 then, but they refunded about £350 on return of the knackered one. Shipped it to our garage of choice and collected the old one after a phone call to say all was done and put the refund back on the credit card the next day. Seemed easier than ebaying something so big, heavy & expensive to someone who could have bought it and not really understood what was wrong etc and risking a negative feedback.
The engine has been great, never missed a beat and is quick too... and came with an unlimited mileage warranty (for 5 years I think, but can't get to the paperwork to check that right now).
We also ended up buying a complete new exhaust as the old one had welded / rusted itself to the heads after 20 odd years so you might need to factor that extra cost in too.
All in all NOT a cheap option but for the peace of mind and very smooth running I think it was the right way to go as we're planning on keeping the van for a very long time - still payiing it off on a 0% interest card which softened the blow a lot
Andi