There are 64 bit Alpha hardware simulators, there is a FOSS version you can download and utilise and see if it does what you ask. It requires a 64 bit host system of course.

You can ask Swiftbase if they have a hobby version of their Charon Alpha simulator. Each CPU in the emulated Alpha must have a dedicated Intel core plus two more, one for the host o/s and one dedicated to the Alpha emulator itself. I have installed/migrated many of these in my time. If you chat to Bob at Swiftbase don't get too enthusiastic as he tends to charge according to the enthusiasm shown by the client. If you are a potential customer he may give you a short term trial key and if I remember correctly they did have a hobby Alpha emulator. If I can find the version I used to use I will let you know. If you get this far I could help you set it up as it can be tricky.

Then, if you manage to get to this point you would then need to obtain the Windows for Alpha software installation and a PAK to authorise it. Then of course, the same for VB6.

In all my time working with Alphas I have never come across VB6 for 64 bit Alpha on Windows, I hope this was some help. I wish I had more knowledge to impart.