The best advice for what you want to do might not be something you're anxious to hear... but if your bike is reasonably complete, try to do your café conversion without cutting any permanent parts like frame sections, tabs, etc. as the resale value will drop significantly. If you plan, as I did, to keep the bike for the duration, then it's fine... but if there's a chance you'll want to sell it in the future, it will bring significantly more money and be much easier to sell if it's stock. Craigslist is full of attempted café builds that people gave up on but somehow think is still worth what a decent vintage bike is normally worth, and most of them go unsold for the dollars they expect. There are many here who have done conversions with little or no permanent mods, and they'll be along soon to share their thoughts and efforts