Got a complete 3tj rolling chassis minus engine carbs and airbox basically.

If I can source a thundercat engine loom Cdi headers and carbs am I missing anything major to complete, other than a 3tj airbox and the conversion plates from kayla, link pipe and can?

I've read through the conversion thread and think I've got everything I'll need.

You could do with a 600 airbox to cut up and mount the 3tj one on

So best the graft the thundercat and the 3tj air boxes together.

Which base and lid do you use, guessing tcat base with 3tj lid.

Wasn't sure if you couldn't elongate the holes in the 3tj base from what I'd read.

I think you cut the bottom of the 600 box out to fit around the carbs then graft the 3tj box onto it ... not sure which snorkel to use but start with the 600 one

i got a 3tj box with opened up holes for a 600 conversion from Kayla - i opened up the holes a bit more and put a bit of rubber strip round the inside of the holes, so the airbox is a good push fit onto the carbs. That works ok - it did come loose a couple of times before i used the rubber and the bike struggled to pick up revs.
Another 4/6 of mine uses a 600 base trimmed down, with a 3tj lid, swathed in duct tape to seal the gaps. i've used 400, 600, and FZ750 snorkels and they all drive pretty well.
Without the snorkel i was always having to tweak the size of the airbox inlet aperture throughout the year, i guess air pressure varies with weather/temperature....?

I'm surprised they're that sensitive to the air box throughout the year, sounds like a tuned two stroke to me...
BANG!

i think it was just the fact that the snorkel wasn't there - once it was re-instated the bike ran fine no matter how wet/cold/hot.