Ok before you start laughing, there is a bit of a different situation that causes me to even ask about this. :-)

First off I live on Big Island HI, options and choices are severely limited here.
Second, I'm building an engine from bare block and crank to new or better specs, fuel pump rebuilt with 7.5mm elements, new pistons, rear sump and oil pump, custom manifold, hybrid K-14 turbo, complete head assembly replaced & rebuilt, was a #14 casting, so need new precups, electric water pump, relocated oil filter assembly (keeping factory oil filter assembly).

So even if I stay 603 turbo, most of the original engine isn't going to be used, plus a #22 head is pretty spendy, because need to buy everything for head.

If I could locate a 606 turbo engine here, I would just rebuild it. But I lucked into a 603 turbo engine so have block, crank and fuel pump to build from.

Parts especially performance parts are easier to to find and are more options.

From what I understand the turbo blocks are the same but the 606 has bigger or additional oil galleries and the cranks are the same.

I'm not trying to convert a car from 603T to 606T, Im building a custom engine for a custom vehicle.

If the 603T block isn't able to be built into a 606T I'll just stick with the 603T and find a #22 head, but thought I'd ask.


Cheers, Allen