BNR34 WELCH plugs come in two flavours:
01648-00121 PLUG WELCH - There are 7 of these on an R34 GTR
11051-D0101 PLUG WELCH - There are 3 of these on an R34 GTR
For the gaskets, if you're doing a lot of gaskets you want the engine repair kit: 10101-24U28 or the gaskets by themselves are:
16175-05U70 - GASKET THROTTLE CHAMBER - There's 6 of these
14035-05U10 - GASKET INTAKE MANIFOLD, B - There's 1 of these