With 60K+ miles on the stock internals, I would forge it just to be safe. 400 rwp is over 450 flywheel and that's too much on tired internals. As a matter of fact why not get a forged stroker kit to add to the displacement? By maximizing the N/A power of the engine, the boosted power will increase as well and the internals will already be forged. I would keep the compression below 10/1 and then add the TT. As far as the actual stock block itself, it can handle 1000hp. So just to be safe and have a backup engine, why not take out the current stocker and keep it in your garage and then have the TT added to a forged aftermarket short block? That would allow you to push this power to 750rwp and beyond.
One thing though is what do you intend to do with this car? Because for road racing, a boosted engine with over 600 rwhp will be hands full and will require some serious driving skills to not look foolish compared to the 400 N/A engines making their way around you due to having more managable power in the curves.
If you want to drag race this sucker, then go ahead and push the power all you want since you won't need to turn and handle. With current weight of the stang and 800hp at the flywheel you should be able to see the low 10s or high 9s at the track.
My 2 cents.