I would have to agree with cockroach and would go with orifice style in this case. 2" sch 40 simplex or even OFU if you are not changing the plate at all are the best bets and with a cost of approx. $800.00 per unit well below any others.
I am not sure of your working pressure but at 1440 psi the meter run size is 4".
As far as being used for custody transfer. They have been and are used for this for years. The new AGA / API spec for meter runs using a flow conditioner bring better acuracy and still can be used in non normal...
1) The companies that build meter runs do not prove them as this is near impossible and the cost can not and could not be passed on to the buyer.
2)Meter runs (tubes fitting etc) are built to exact specs with very little room for mistakes to codes that apply eg. AGA 3 API 14.3
3)The codes...
