Stock internals are plenty sturdy for 300+ (well tuned) WHP with either an e or i motor. I'd boost the motor you have as is, but consider upgrading the headbolts depending on your power goals.
I'd argue the easiest swaps are M50 swaps from E36's, but some argue the value of the swap.
The M30 swap isn't "super" easy, but it's far from rocket science, and mounting kits are available. Tq is nice, and they LOVE boost.
1998 328i "M-tech"
2001 TDI Golf. 1300km/tank commuter. Boring, slow, cheap.
1991 P-car: 964c4 Let the porcupine jokes commence.
Gone: '99 M3 vert, '98 M3 sedan, '91 E30, '89 E30, '87 E30, '91 Euro M5, '93 6-speed Corvette, STI v8 swapped '98 Impreza, '73 2002, 2004 325iT