Does an 89 GTA require 21 or 19 rated injectors.
Holley's catalogue shows that there are two different parts numbers for 89 305's. One is the same as the 350 which I'm guessing is larger than 19.

Would there be any harm in installing 21.hr injectors on my 89 GTA?
The car is stock with freed up intake and exhaust..

 

Steve, your engine stock came with 19#'ers.

Running 21 (at same FP) may cause it to run rich at WOT without some EPROM runing...yes you could lower the FP to compensate at WOT, but then spray pattern isn't as good, possibly (maybe not) affecting part throttle.

 

I'd go with some 24lb injectors. Of course you'll probably new to change your prom parameters.