20 blocks are Ok and most from around 1981 onward should bore to 93mm though I wouldn't go further. The 205 block should bore to 93mm 100% but I still wouldn't take one further as there's just too much blow-by when these engines are stretched.
Having a big turbo on the 205 cossie (selected and measured blocks) Vs a boggo 20 makes little difference at standard bore sizes unless you go over 500bhp, and even the 200 struggles over 600bhp on racers with blocks being 'lifed'
after only 20 - 30 hours!
Fast road spec to max Ford oversize should present no probs and if it does then that block was a dud anyway....
HTH BV.
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