The bike you are asking about does not exist. It comes down to what do you want and what is available.
For a great Cafe bike, start with Triumph. Norton or Triton. They embody teh cafe racer spirit better than anything else. But they are not cheap or 4's.
Stylistically, 4's don't make great cafe racers because they tend to look fat where a cafe racer should look svelte. That's not to say it can't be done, but this is where it gets to what is your vision? Search the web and come up with a few that talk to you. Long breadbox tanks were great when engines didn't make much power and handling was not understood. Airtech and Glass from the Past (among others) make a variety of long tanks for many different bikes and in many cases they are close to the original styles. Others like Legendary or Benjis Cafe Racer also offer tanks.
For a great tank, think about a custom made alloy tank form ROC city or Asa Moyce at Bartel or John Williams at the Tanks Shop. For a Honds tank, talk to Pete Kyte in the UK. There are others. Budget 500 for a glass tank and 1200-1800 for an alloy tank.
If it must be a 4 look at what's available in your neck of the woods and scour the internet for pictures of modified versions of the bike to see what works and what hurdles there are.
On the other hand if you want to buy a bike, go to a catalog for parts, add paint and polish and flip it, I would suspect that not a lot of people are much interested in helping you to make money.
BTW, back in the day, we rarely cut frames and we "made it our own" by bolting on parts from Dunstall or Bil Chuck or Gus Khun or Reads. No one made their own tank or seat. We rebuilt our bikes with whatever parts we could afford and wanted. And we just kept riding and upgrading and riding and changing and riding.....Rinse and repeat. YMMV.