'Second - the air box: Don’t really want to use pancake filters so possibly metal fabrication but probably fibreglass. I will have to make a plug/former and mould first which will be tricky enough. Going to have to be in minimum 2 pieces and need to get pipes for air intake and breather sorted out, then bond 2 pieces and pipes together. This I suspect is going to be a longer messier job than the manifold!
It will probably be Christmas or 2019 before this part is anywhere near ready.'
I have fitted an airbox as in the link below to my lotus Europa with twin Dellorto 40's and I can highly recommend it both for noise reduction and professional appearance. I bought mine with an undrilled baseplate so I could make it fit my non standard carb placing. The narrower version should fit in the tight Murena space available.
https://www.thepipercrossshop.co.uk/pipercross-px600-airboxes-including-feed-pipe_p23378572.htm