Michael,
I’m no expert but I have made some improvements on my 403 over the past 11 years which may help you to get some ideas.
The brakes will be better with a servo, of course, but my whole world has changed with the servo plus front disc brakes. The discs are visible on close examination but originality is of no value if your car has just rammed another vehicle / wall because you couldn’t stop in time !
I have normal retractable seatbelts located to the B post at roughly the level of the top of the seat squab. This nicely hides the belts when not in use but ( as I found out later ) has the drawback of pulling on the shoulder due to the retraction spring. I have cured this problem with a neat little plastic gadget called Klunk Klik, which holds the belt slightly loose once adjusted but allows full functionality.
Agreed that the semaphores are useless. The problem is that, even if they work, most drivers of modern cars haven’t a clue what thay are for. The standard rear indicators are poor because a) they don’t face backwards b) the reflectors are poor or non existant. I had custom built fibreglass pods made and fitted to each side of the spare wheel tray. Although not original, as with the brakes I think that it is more important not to be rammed up the back. Not to everyone’s taste, but here they are :
https://picasaweb.google.com/drdavedale/403Indicators#
My front indicators are 21 watt amber bulbs in with the sidelights and these also double up as foglights. Please see the above photos. I know of a Bristol 400 which has a dashboard switch which allows the driver to select his modern indicators OR the original semaphores to indicate his turning intention.
BTW, you didn’t ask about brake lights but, for what it’s worth, the same problems of angle of the rear light assembly and the reflectors apply to the brake lights. With my rear indicators now separate I have two 10 watt brake lights on each side in the assembly with the whole glass painted red with glass paint. I also have a brake light in the rear window which is fairly inconspicuous when not lit.
Rear view door mirrors in classic style are readily available which clip into the forward verical guide channels of the wind-up windows. Giving a much bigger and better rearward view than wing mirrors because they are closer to the eye, they do not interfere with the movement of the window and they look good in chrome. I suggest that you may consider putting one on the nearside also for driving on the continent.
I had the same problem with the spark plug caps falling off. Problem cured with the removal of the plug nipples and different HT lead clips which slide onto the plug threads with a satisfying push and grip very well.
The wipers are a known weak point. Several 2-litre Bristol drivers have arrived at their destinations without one of the pair of blades with which they set out. There will be others who disagree with me but I think that the chuck that grips the blade to the spindle is of a poor design and my own often need tightening. If you remove the LH blade and satisfy yourself that the spindle is reciprocating correctly, I suggest that you refit the blade and tighten the chuck. It is very easy to strip the thread so please be careful.
Good luck !
Dave Dale.