Pine Engineering built my MK3 but the cost of shipping back and forth from NZ might negate any savings over the cost from Love20Bee. Mine went from Japan to NZ to US.

Barrels alone are close to $2k since you need both halves. Love20Bee has asserted themselves at the top of this market in the US and can command a premium but since the RS8 are front mounted and yours don't need to be split, it shouldn't be a difficult job. I would definitely weld them though.