Wow mate, that is going to be quite some starter jet project.

However, anything is possible.

I think you can expect some help if you gave us a bit more information, For instance:

Are you going to build it from a kit? And if so, which one? If not, are you building it from a set plans? What are you planning to make the various diamensions, if it's scratch built?

I can only tell you that 2 x P120's will power a rather big (and very long) SR71, I trust you've got a means of getting it to your flying site.

Good luck.

Springbok Flyer