i`m about 90% done on this myself....
make a jig and get a flange for the head cut:
roll some tubes cut to size and weld them on:
as for trumpets you can do what sandy does and sit them inside.. or use some hose and clamp them on.. personally i had some flanges laser cut and welded them onto the bodies:
which then let me chose a range of trumpets from jenvey:
the 2nd butterfly spindle holes need blocking up so you`ll need some bungs:
in honesty i`ll probably sack the hose off that joins them to the manifold and weld some more flanges on...
basically its a LOT of farckin around and if you aint an engineer its probably easier to just phone colin/sandy and get there kit..