Spoke to owens development via email today on the subjects of turbo's heres what they said:-
Reply 1:-
The ODGT2868HTA-M with the T25/5-bolt turbine housing would be £1,346.77+VAT. The price is the same for the .64 and .86 A/R turbine housing options. The .86 A/R housing is almost never used though, we were curious as to what you have in mind for the turbo? We might have a different solution for you.
Reply 2:-
The turbo’s you’ve mentioned are exactly the ones I would have recommended, the only other thing worth considering would be using an external wastegate, though you’ve said you’re not changing manifold so that doesn’t seem possible.
The GTX2867R would be quite well suited, the downside being the compressor wheel is larger than the 68mm HTA (we disagree with Garrett on where you measure the compressor exducer) so you would lose a bit of spool relative to the HTA, but would have more power potential. The 68mm HTA wheel is rated to ~480hp so you still have some power in hand. To maximise the spool I would recommend the .64 A/R housing, it won’t choke your turbo and limit the power, but it will improve the spool a lot.
If you have any more questions let me know
Reply 3:-
The GTX2867R is £678.53+VAT, the housing is £136.78+VAT. That price doesn’t include an actuator or bracket, which will be ~£150. If you wanted the turbo in M-Spec (like the quote for the ODGT2868HTA) it will be an extra £276+VAT.
GTX2867R - £815.31+VAT (~£965+VAT including actuator/bracket)
GTX2867R-M - £1091.31+VAT (~£1,240+VAT including actuator/bracket)
M-spec turbos look tempting till you see the price lol