I'm going to assume you are about 17 or 18 as you've not mentioned your age.
The non-standard engine could prove to be a problem in getting insurance. Some insurance companies may be okay with it, others are not. I'm with Footman James and they have a restriction of a 25% power increase over stock for 21-25 year old drivers. I do not know if it applies to 17-21 as well.
Reliability of a Series is entirely down to its condition. They are all very old now, and most were used in a commercial environment for years. This means many are fecked or have been put back together badly (e.g. poor workmanship or quality of parts). But even in a very tired and worn out state they are generally okay providing you are happy to work on it as and when needed. That may mean for the first year of ownership you could be working on it every week to keep it going, with it gradually getting better as you fix all the previous owner bodges and parts that have expired - or you could have a trouble free year of motoring with mild maintenance if you're fortunate.
You can change body types as you wish too. So you can fit a hard top as you would like, and you can fit bench seats with relative ease.
In my own opinion the vehicle you've linked to on Ebay looks pretty horrid on the surface, but I guess if that's your thing.
Oh and don't get drawn into the shiney paintwork and bling - there are lots and lots of Land Rovers that have been tarted up but are still a turd.