^they had a 420ztt?
Was it a yellow z?
Only one shop is making the 4.2l stroker kit and IIRC its GTM in Cali.
If GTM built that block and tuned the z, dam thing would be hitting 600+whp on low boost as a DD, high boost would put it upwards of 1000+whp.
Alex,
As far as I know, GTM does not make/sell a 4.2l Stroker kit for the RB26.
Church