A few thoughts
That is a very nice car. I too would love to have it and race it. But there is simply no way it weight 750 lbs.
I should note that 750 kg x 2.2 = 1650 lbs. After looking closely at the photos I would believe that number. I have built a number of X1/9 racecars as well as others (my MR2 among them) and know that by the time you have the driveline, lightened chassis and cage, tubular suspension, custom uprights, lightened bodywork, and ancillary systems, you seem to end up in that 1600 to 1800 lbs range depending on how extensive the build is.
Add to that the modern Alfa 2 liter and transmission and you have a very slick car. It would be big fun.