Steer clear.
The P38 engines are finicky. All Al block with Fe sleeves that are prone to failure, i.e. "dropping a sleeve".
Is it JUST a blown head gasket or are the heads warped? If the engine was overheated for an extended period... you should suspect a dropped sleeve. Therefore a suspect engine.
There are plenty of used P38's on the market with reliable engines... go for one of them with a good service history and single ownership. Carfax should be able to assist; little money upfront saves expensive repairs later.
Good luck,
1990 RRC, 3.9L, AUTO "Willow Pond" (Sold)
1996 D1, 4.0L, AUTO "Lucas"
1999 RR, 4.0L, AUTO "Belle" (Sold)