How do you make your Peugeot 504 more stable at high speeds?

What I have done to my 1974 T.I. is ;

Fit the 505 alloy wheels 15 inch by 6 with any good quality 195/60 series tyres (205 size I think is too big for the rim, the tyre tends to walk across the rim width and under hard cornering the tyre tends to rub against the front strut ). Start with tyre pressures 30 lbs in the front 32 at rear and work from there keeping 2 lbs more pressure at the rear than front. With my car I have lowered it 3.5 inches which is I think the maximum you can get away without altering suspension pivot points. Now you will have negative camber at the front wheels so alter the front wheel toe in to no more than 2mm toe OUT. Lastly and very important.... At the rear brake pressure regulator which works off the rear anti roll bar unscrew the adjustment one turn for every inch you lower the car. Unaltered the regulator thinks you have a full load and gives you full brake pressure to the rear brakes...... sideways with rear brake lock up at 160 km is not pleasant !!. I am assuming that the shock absorbers / stabilisers are all good.

Watch out for the little "kick" you get from the rear end when going over bumps on high speed corners. All good fun !. Lower the car, add a spoiler, low profile 18" tyres and a phat bodykit!!! Add rear stabalisers