All, this thread and process has been a long one. I've made some mistakes and learned along the way. Took much longer than I anticipated and we've had some hiccups and an item which is unresolved-gaskets. End result is beautifully crafted T304 stainless equal length long tubes that are unique to our LSx Z's.
Unfortunately I do not have control over the process any more that you do and it has, at times, been frustrating.
1. Discovered the 'floor' difference between the 240z and 280z chassis which prompted me to 'adjust' my right side header [i do not hold the builder responsible for this one by any means as he is not a Z guy].
2. We have no OE multi-layer manifold gaskets-yes, they are part of what we agreed to with the builder. I have [and others have too] asked repeatedly but without resolve. Personally I am re-using my OE gaskets with the hope the original agreement will be met.
3. My right header does not fit with my OE F-body 2001 starter installed. I have learned that SUNNY Z's engine had an aftermarket [slightly shorter] starter installed but was not aware of this nor did the builder notice. I know, by sight, the difference between a Z and ZX OE starter but not a GM.
4. I shipped my right header back to Blake to ensure it fit the original build jig [it does] and ask him for a solution. He stated that using an LS2 factory starter fits fine and sent me pics showing clearance. My header should be on it's way back to me shortly and I'll either modify the header [as JustAFantaZ did] to fit my LS1 OE starter or purchase the LS2 model [or what SUNNY Z has]-not sure which yet but am leaning toward header mod.
Hindsight: have 2 Z's there-240z & 280z & ensure the 'mules' had stock LSx components and finally, understand that it always takes longer than it does...