John a 105 in good condition is a perfectly suitable car as a daily driver due mainly to their advanced design. The power, economy, braking and handling all match the performance and keep up well with modern cars. They are also a reliable proposition being mechanically uncomplicated compared to many other late model cars.
Reduction of air noise however is very very difficult, a good stereo may be the answer there. Suspension improvements with adjustable shocks etc are easy. Contact Pace Engineering 98440147 for all your needs. Also don't under estimate the benefits of good quality tyres. Seats can be changed or re-bolstered for improvements and air conditioning is a valuable comfort item but a little more difficult to have fitted.

Hi John,

I agree with what Gary said but would add that I think the unreliable parts of these cars are the smaller items.  I've had mine stop a couple of times but it was because of loose wires and blown relays.  Check the groundinging points and make sure they all have good contact with the body.

The cars are well designed and built but after 40 years you will find that components wear out or fall off if not checked.

I've heard electronic ignition makes them run better and be more reliable but I'm not sure myself.

Like yours mine runs better now that it is being used so I think they appreciate a bit of care and attention and they get bored just sitting around.

Andrew
Oh, and being nuts is great.  It lets you enjoy your drive instead of dreading it like "normal" people.  Smiling is a sign of being nuts so go ahead and be nuts.

105 as a daily driver, not a problem, a bit of pre-emptive maintainence is all you need.

Electricals
As everyone has said so far these are what will let you down.  First thing to do is rip off the starter motor and the alternator and send them away to get re-built

Ignition- whether you go down the path of electronic ignition, great for starting on those cold winter mornings before work, make sure the rest of the ignition system is in good nick, a few things that are cheap and quick to swap are, ignition leads, points, dizzy cap and ballast capacitor, and possibly a new coil, and one very simple upgrade that cost almost nothing is making a new connecting wire from the points to the coil with nice new spade terminals that wont fall off when the engine is running.

Lights- WD40 is your friend, go around the car and pull all the lenses off check all the globes give all the contacts a squirt with wd40 and put them back in, if lights still aren’t working its likely to be a problem with the fuse box or bad earth connections.  All the lights have terrible earth connections to the chassis that get affected by rust.  Pull the light fitting out clean the mounting studs and the chassis where they attach with a wire brush and give them a spry with WD40 before you put them back in.

Fuses - Go through the fuse box rip all the old fuses out, check that they are the correct spec hit them with some WD40 and before you put them back in give the mounts a squeeze with your fingers to give them a but more preload to hold the fuse in place. 

Relays- these cars never had them (except on the horn and the rear demister on 2L).  When I was building my red one I measured a 4 Volt drop just across the switch gear for the headlights, properly installed relays on all the lights makes a massive difference to the quality of your headlights, once you have done this and put some decent globes in the 105 headlights are actually very good.  If your adding relays its also worth putting one in for the starter motor solenoid.

Suspension
A set of new shocks (koni) and some new bushes either standard or nylathane will make a massive difference to the ride quality, especially replacing the cone bushes on the t-piece.  Up Front Checking and replacing if necessary the six steering tie-rod ends will give the car a much more precise steering feel another thing that can affect this is the steering box make sure that all the bolts holding the top cover on a very tight.  Obviously checking all the suspension joints is important these are just the ones that are generally worn

Engine
The only problem you will really have is head gaskets and you will only have problems if the cooling system is faulty.  Take the radiator out and send it off to be cleaned, get a new cap and make sure the overflow bottle is not blocked.  Use some coolant in the system and bleed it properly and you shouldn’t have any problems even on the hottest summers days

I’ve had various 105's on the road for the last 10 years there great fun and as long as you look after them you shouldn’t have a problem.