I currently have both engines sitting in my garage. Now the question is which do I go with to build and swap into my 87 Iroc-Z? I want to build either one into a 383 Stroker. Which would work best with my current tpi setup?

 

Neither Engine will fit the TPI Parts.

However there is a TPI Lower Intake-Manifold that is made to fit the Vortec 350 Engine/ Cylinder-Heads.
Nothing is made to do so for the LT1 (Gen-II SBC Version)...
The stock LT1 (Gen-II SBC Version) Intake-Manifold out-performs the TPI Intake-Manifold anyway.

There is more Aftermarket support, and more Parts flexibility for the Vortec 350 Engine...
And is slightly easier and less expensive to build for more power.

I rarely do any LT1 (Gen-II SBC Version) Engine builds for my Customers anymore...
But when I do, there are 2 major changes that I make.
They are requirements... or else I tell the Customer that I will NOT build the Engine.

First: the Opti-Spark Distributor Design is too unreliable...
and must be replaced with a Gen-I SBC Distributor, a Belt-Driven MSD Distributor, or converted to Distributorless Ignition.

Second: If using a 4L60E Family Transmission, the Original PCM and Transmission Electronics operate too slowly...
And must be updated to later Model PCM and Transmission Electronics, or Aftermarket Control.


Good luck and have fun!

 

There actually was an Accel Gen II SBC TPI lower intake manifold base that allows you to run GM style TPI, Accel Street Ram, or Accel Super Ram on a Gen II SBC. Also made a shorter Super Ram plenum for the 4th Gen F body.

 

Having both, I’d say build the Vortec. Are you planning on using the stock heads or going aftermarket? The rotating assembly can be the same between the 2 but the top end of the Vortec build will be a bit more flexible. Aftermarket LT1 heads are expensive and intake manifolds almost nonexistent but Advanced Induction still ports factory LT heads and produce pretty impressive numbers with them for about the same price with manifold porting as AFR Eliminators. Add another $2000 if you want to go distributorless but I personally haven’t had issues with my optispark. It won’t be much cheaper to get the Vortec’s induction sorted if you want EFI, port or throttle body with it. So it’s kind of a toss-up unless one of your blocks is a factory 4-bolt.

 

If the LT1 is an aluminum headed version, send those heads off to Lloyd, or Advanced induction depending on your budget. They port pretty darn well.

Vortec leaves you open to the same SBC head options, so you are an aluminum head swap away, and you have quite a few aftermarket choices.

LT1 locks you into LT1 and the aftermarket for that is fairly limited compared to SBC. There are less choices overall.

The Vortec Iron heads are basically the same thing as iron heads LT1 heads.

 

if you arent planning to make massive n/a hp, i think i would set the LT1 up with 24x and holley terminator. seems like it would be a pretty easy swap, and can make well north of 400whp with head porting/cam/valvetrain. you can run a ported stock LT1 intake to over 500whp. a sbc intake can be fairly easily "adjusted" to fit onto an LT1 also.
If you want to make really big n/a hp, you will want to stay sbc.