Hi Paulo,
Welcome from me (us), and thanks for your intro and this thread. Your project is a useful reference for mine. I have had about 4 years of teething (now more sorted after sleeving and new IMD pistons/rings). I have a '58 Flash also, still with iron head, but way less correct cycle parts. Your overall finish is great yet practical. Your main jet compares with my 310, that I had to go up to - still with air cleaner, but custom reverse-cone mufflers (less baffle). I have the 1 5/32 new Amal 389. It now powers into higher revs, in the full-throttle range - where it started missing and fading, with a 290.