No worrys mate, as far as the block goes there is not much difference between a std block and a STI "tuned" short block,
if memory serves only real differences are; head gaskets, pistons, wrist pins and some later models have a billet crank vs the forged equiv. both however have a more refined balancing than stock.
Most of the STI goodies are bolt on ancillaries, I mean in terms of comparison there is only 1 difference between the man. gearbox and short block of my non-STI GTBL and that beast..... the wrist pins.
Hope I helped a little tis a nice car and a fair price too...