My D1 was the first diesel I owned. From age 15 to 40, aside from daily drivers, I only owned small British and Italian cars. The only exception was a Toyota FJ60 that I still kick myself for selling 20 years ago.
Then marriage and child came along and the 2 seaters had to take a back seat... pun intended.
I really liked the look of the Defender but couldn’t bring myself to spend Defender money on a glorified tractor. I learned a D1 where it matters is essentially a Defender. And, unlike the Defender, it has some safety features and is a lot more comfortable to drive. I’m not hating on Defenders, I’d still like to have one.
I also wanted something less electronic than a modern vehicle that could sit idle for months and live at our cabin in the woods, so we could have 2 vehicles on our infrequent visits. Diesel is much more stable that way. You can also run the 300TDI and it’s mechanical injection pump with nothing more than 12 a volt power supply to the injection pump and starter. When I leave the cabin with months, sometimes 6 months between visits, I just disconnect the battery cable. When I get back, I reconnect it, and the simple diesel cranks over a couple times and fires right up.
I also really wanted a manual transmission.
D1s were cheap and I wanted an interesting new project. Found a rust free one with a bad engine on craigslist in AZ, and the project began. It was a learning project. Most of my knowledge of the conversion came from another forum focused on Defenders.
I later bought a Santana (Defender / Series clone). It has an NA diesel that makes the 300tdi seem powerful. I have a 200TDI set aside for it as a someday project. That NA diesel is good for nothing (well not that bad really) more than crawling around in the woods. It’s an unstoppable beast at 10mph.
If you don’t drive on the interstate much and live in a fairly flat area, a 300tdi with 5 speed is a pretty simple swap that will serve you well. Adequate power around town and will do 70 no problem on flat interstate. However, even slight long grade increases and you struggle to keep it at 65. You can spend some money to improve performance, however.
I later bought a GMC Canyon diesel for regular use which has plenty of power but I doubt would buy another modern diesel. The emissions requirements make them overly complicated and prone to problems.
I spent too much on the 300tdi conversion because I did it when they were all the rage. Now, they are yesterday’s news. I recently bought an R380 gearbox to pair with the 200TDI set aside for the Santana for $600 that had only 5000 miles on it since it was installed in a Defender as part of a 300tdi conversion. The seller pulled both to put an LS and automatic in.
If you have always wanted to do a 300tdi conversion, now is a great time. One thing to note is the Defender gearbox won’t work in a D1 without modification. If you already have a 5 speed D1, you can combine the Defender R380 with the D1 V8 R380 but it requires swapping / combining bellhousing, shifter parts, and input shaft in a combination dependent on which one is your “base” so to speak. If you are not comfortable with doing that, getting a D1 300tdi gearbox isn’t horrible expensive. Maybe your R380 is tired by now anyway.
Being the hoarder I am, I have a spare low mileage V8 R380 set aside and picked up a 300tdi type input shaft and associated parts to do another conversion someday. All of it acquired pretty cheap because I wasn’t in a hurry.
Also, starting with a 5 speed D1 makes a lot of sense as the D1 5 speed interior parts and pedals are very hard to come by when not attached to the whole vehicle. It’s well worth spending the extra dollars to start with one already a 5 speed.