There is a lot to be said for keeping Peugeots in original condition; but sometimes there are good reasons to depart from the straight and narrow.
However in the case of the 404, I see opportunities for savings in running costs and improved performance by incorporating ideas from later model Peugeots. My favourite modifications are:
| Upgrade | Pluses | Minuses |
|---|---|---|
| 404 pre 1969 | ||
| Upgrade to 1969 or 1970 model brakes and gearbox. | Servo assisted disk brakes, load sensitive rear brake limiting valve, excellent gearbox. The 404 was a world beater in 1960 and it was even better towards the end of the production run. | Nil. |
| 404 | ||
| Install a 2 litre engine. | More power, potentially better economy, cheaper to purchase and repair, very easy to fit in 1969 and 1970 models. | Noisy, sedan diff ratio is too low for the engine and it is difficult to change. |
| Modify 15 inch rims to take cheaper tyres, e.g. change to 14 inch diameter 6 inch wide rims. | Cheaper tyres, better handling. | Lower gearing leading to more noise. |
| 404 Commercials | ||
| Install a taller diff ratio (e.g. from a 504 wagon) together with a 2 litre engine. | Reduced noise and more comfortable cruising (overcoming the major disadvantages of fitting 2 litre engines). Very easy to fit in models from 1967. | Nil. |
| Install 504 wagon hubs and brakes together with a 404 sedan disk brake master cylinder and brake booster. | Disk brakes, 504 wheel stud pattern which allows a wider choice of wheels and tyres. Parts are widely available and cheap. | Nil. |