I'm sorry to say, but go with the S-trim as many A-trim users do. Expect to see about 5psi or so with a stock A-trim blower. You'll see less boost than a stock motor because your motor is more efficient and flows more air.
However the horsepwoer will still be there. With the use of a powerpipe you can bump it to abotu 8psi or so. By changing out the 3.33" pulley you can see as much as 10-12psi, however the A-trim is not meant for 10psi or over and will wear out MUCH sooner than it should. I had an A-trim on my car for a few years and added a powerpipe, seeing 9psi. The A-trim lasted all of 6 months after that, then spun a bearing. I had asked Vortech what I could do to see more boost, like a smaller pulley, but they told me just to have the A-trim upgraded to an S which I did.
If you plan on running more than 5-6psi, then get bigger injectors, and an MSD 6BTM. I know you said you already had a Timing Master, but you didn't say if it was an actual ignition or not cause mine is separate from the 6AL.