Modifcations can add value to your truck, or take value away. It depends on the modification, the quality of the work, and most importantly who the prospective buyer might be.
Radical modifications are more likely to cost value than easily reversible ones like you propose. If a prospective buyer is looking for a driver rather than a show truck, an alternator and HEI will both add appeal. A generator and points will not.
I absolutely disagree with the suggestion that a points type ignition is more reliable than a modern electronic not just because of the work required to maintain one, but because some of the pieces must be replaced much more often than the corresponding parts on a modern electronic.
If you buy quality parts an HEI will serve easily for 100,000 miles plus without the cap ever being removed. You can't make that claim about any point type ignition.
