Generally speaking the ideal choke size of a weber/dellorto is based on teh size/rpm range of the engine and what size choke is required to develop sufficient signal strength to allow decent fuel metering across said range. In simple terms they have to create a (albeit not massive) restriction of sorts, to manipulate the air velocity through them (and that causes the small pressure drop that gets fuel flowing). So not having ot worry about that, since fuel is delivered in appropriate amounts and somewhat effectively atomised/distributed by the ECU/injectors, you can go a little larger without any real loss.

What you'd ideally want to do is to run the engine with 40 then 45 (of course this costs a lot) throttle bodies on there, and dyno the engine and in particular look at the intake vacuum at peak hp/peak rpms and through from 2/3 to full throttle. Ideally you'd want to find hte size that just avoids any significant (in this case perhaps 0.75" Hg tops 0.25-0.5 more ideally) vac at full throttle. If you ran bigger tbs, it might get full VE with only 3/4 throttle. It wouldn't affect output per se, but you ideally want to just get it at full throttle, that want you can map from 1/2-3/4-full throttle well. If it makes full VE by 3/4 throttle, then even if you lift off the throttle a little, it won't drop power, and you have far less fine control over the output of the engine, which is vital for mid corner and corner exit especially

Having said all that I'd probably suggest trying 42mm if they actually exist, or if not, and it was between 40mm and 45mm throttles, I'd probably just give the edge to the 45mm - but that is speculation from me.