I'd like to express interest in your internal fittings (my spare Ferret is missing heaps of bits) and your engine, if you do get around to changing it over. PM me if you're keen.
When I first got my Saracen, I wanted to convert it to a diesel, but I've learned to live with, and love, the B80.
Some Ferrets in British service were fitted with brake boosters, one of those would be an easy retrofit to yours. It won't give you fantastic brakes, but it will be better. Also note that the Ferret brakes are manually adjusted. If yours aren't set correctly then they will be awful.
If swapping the engine, you'll need to be wary of rev ranges - the B series redlines at 3750 RPM, which is quite low for a modern petrol engine and quite high for a diesel, making them hard to match. In all honesty though, the Ferret has reasonable power to weight, and a properly maintained B60 is very reliable. If I were going to modify a Ferret to have better performance, all I would do is fit a smallish turbo to it; with its relatively low compression ratio and slow running, it should add an extra 50hp with no stress at all, although a water to air intercooler may be needed.
Noise is always going to be a problem in the Ferret, no matter what you do to it. You're sitting between a pair of drive shafts and the shape of it puts you near the focal point of a bell shaped interior. They're surprisingly quiet on the outside and surprisingly loud inside. Padding may help, but it's hard to say. I just wear a headset. If you do fit padding, make sure that it is fire retardant and doesn't off-gas any toxic chemicals. Fire is a real threat in the Ferret.
For the seat, the early Ferret seats suck. Later ones in British service were fitted with the same seat as the Fox, and it is more comfortable and offers reasonable lumbar support. I would be very wary of a bucket seat in a Ferret, especially a Mk 2, as it will hinder you getting out in a hurry, if you need to.
For bead locks, you'll need to replace the rims, I would think. I doubt you'd find anything off the shelf to fit a Ferret, so you'll probably have to go custom, which will be pricey.
Cheers,
Terry