I found a 355 small block that i can purchase i want it to be fuel injected can i use my 5.3 pcm and reprogram it?

 

yes but it's alot of work involved.

 

what would be the best thing to do

 

You can use a 411 PCM and using a calibration file for a 2001 or 2002 Express van that had a Vortec 350 in it to control your GEN 1(I assume) to control it.

You will need to use a- Vortec 4.3,305,350 or 454 distributer with a Vortec 305,350 or 454 dist cap on it. With the Vortec CMP sensor installed
-Intake manifold that fits your 355's heads that will hold 8 fuel injectors
-8 high impedance fuel injectors
-Vortec 305,350,454 throttle body
-MAP sensor
-Vortec 4,3,305,350,454 or LT1 LS1 75mm MAF(with modified MAF frequency table), or use an 85mm MAF from a 99+ 4.8,5.3,6.0 truck or 2001 and use teh stock Van MAF frequency table as teh Express van in 01 and 02 used teh 85mm MAF on the Vortec 305 and 350
-plastic front timing cover from a 1996-2002 Vortec 305 350 to hold the crank position sensor
-4x crankshaft position sensor reluctor wheel
-411 PCM with 2001-2002 Express van calibration file installed(VATS delete, and other emissions stuff disabled via tuning) with a 4l60e or 4l80e segment calibration swap installed or set to manual trans for thm 350,400 700r4 or manual trans use
2001-2002 van harness that uses the 2 80 pin connectors

plus other stuff.

Here is a link for Vortec 96-99 OBS truck that use teh Vortec 305,350,454 engines that wish to upgrade to teh 411 PCM.
http://www.pacificp.com/forum/viewtopic.php?t=3240

Basically what I have given you is a way to run a GEN 1 engine that uses a distributer a way to be powered by the 411 PCM.
You can use HPTuners, Tunercats OBD2, LS1 edit, Westers GMT, Jet DST EFILive to tune the 411 PCM with.(I'm sure Ive missed others.)

I'm not sure if your 2000 5.3 truck used the 411 or not.

There are guys as we speak that are modifying a 1999 L21 Vortec 454 with Coil Near Plug ignition to work on teh GEn 1 smallblocks. It works just fine. We are just waiting for them to release the crank reluctor rings, which are the L21 454's 24x reluctor modified to owrk on a SBC beingread by a Vortec GEN 1E 4.3,305,350,454 crank position sensor which is found in the plastic front cover..
Here is the COP ignition on a GEN1 engine thread.
http://www.thirdgen.org/techboard/df...olled-gen.html

peace
Hog