First off, the next move for you would likely involve some engine management upgrades and a larger set of injectors, since any power gains will be severely limited by the stock injectors. Your speed density system is extremely sensitive to changes in engine vacuum, so even a mild cam will adversely affect the way your car runs, unless you make changes to the ECU via a tuner of some kind.
The Moates 1/4 horse would be the least costly way of controlling the ECU. Initially, many people are intimidated by ECU tuning, but like anything, it can be learned step by step. Having the ability to tune the ECU, unlocks pretty much all of the performance potential of your engine and will allow you to make future changes to your engine as you build it up.
In order to get the most possible power our of a cam, it's a really good idea to increase compression as well.
89' Mustang convertible, high compression N/A 2.3.
85' SVO under s l o w deconstruction.
93' hatch currently under development