your take on BOV's and WG's

I would guess that that HX40 has a 13cm or 15cm housing on it......Ideally the HX40 you would be looking for would have a 17cm twin scroll.

Or even a HX55 with a 19cm.

I dislike Holset Turbochargers overall because of the lack of "aftermarket support" for them....you have to dig through tons of Cummins Literature to source all the v-bands and such.

I prefer http://www.precisionturbo.net/

I have custom spec'd a couple from them and their support has been Top Notch.

For a Single Turbo 273ci SBM with a target power range of 400-500rwhp on pump gas and under 14 psi with no aftercooling, I would recommend a 67mm compressor inducer, S-cover compressor housing, T4 Exhaust Flange, 70mm exhaust exducer, .96 A/R exhaust housing.

I would use (1) 50mm chinese wastegate on the collector Preturbo.
one with a 7psi spring in it...and get a Manual Boost Controller and a 30 psi gauge to tie it all together and monitor it.

150gph electric fuel pump.
Return style Bypass regulated 1/2 feed/return.
Set at 7psi idling...rising rate 1:1 Bypass Regulator
Holley 750 4150, Blow Through
50mm BOV pre-Carb

Single 3.5" Exhaust post turbo

Wide Band tuned of course

(I would throw in Meth Injection and crank the boost....but thats JMO)

would be a fun ride with a 742 SG and some 2.94's or 3.23's :burnout: