New 350 engine swap for: 1991 GMC Sierra SLE, 4x4, TH700R4, Heavy Duty Chassis Option

Alright guys need help in deciding what NEW engine to use.
After many phone calls to Pace Performance parts in Ohio, I originally wanted to put in their new 350 Vortec Multi Fuel Injection
Premium Kit crate motor: cost $4,395.00
Some of the old wireing for the stock ignition from the original block wont fit/work with that engine.
I then decided that their 350 H.O. might work and or fit since this is just a long block with no intake manifold, but this comes with Vortec heads. I have no idea if my old intake manifold and throttle body will work with this engine: cost $2,219.00
They sell a direct replacement 350 long block: cost $1,554.00, clean up my existing manifold and throttle body and I'm good to go.
I want more horsepower and a stronger motor.
Any ideas guys.
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