97 chevy 5.7 vortec in my 59 chevy truck need help

[bobdavis2010]

Hi!! I need some advice I have a 59 chevy truck with a motor from a 97 chevy 5.7 Vortec it starts right up sounds good revs up but when I drive it it has no power it goes but again no power (codes multiple miss fire) I put new plugs,wires, cap. checked the fuel pressure and has good pressure. I was told the spider spider injectors are bad I checked to see if the fuel pressure lowers after turning the key off and it holds pressure I was told if it looses pressure then that’s a indacation that the spider is bad? Any ideas on what to check?
Tranny-4L60E