The 4-piece engine frame mounts are sold as repros, for around $80, or less.

http://www.rockauto.com/en/parts/goodmark,GMK4320335672S,motor+mount+bracket,11841

http://www.ebay.com/itm/Goodmark-GMK4320335672S-Replacement-Engine-Mount-Bracket-/301874275659?fits=Year%3A1968%7CMake%3APontiac%7CModel%3AFirebird&epid=1023648239&hash=item46491be54b:g:WUoAAOSwFNZWwz8s&vxp=mtr

http://www.ebay.com/itm/1967-1969-F...52370187356?_trksid=p2349526.m2548.l4275

https://www.summitracing.com/parts/oer-k576

Cheap rubber motor mounts are $11 or less, each.

https://shop.advanceautoparts.com/p...GUdoRhO-4BoCV-4QAvD_BwE&gclsrc=aw.ds

http://www.ebay.com/itm/Engine-Mount-ANCHOR-2254-fits-67-70-Pontiac-Catalina-6-6L-V8-/382033421139?epid=79263472&hash=item58f2f76353:g:YgcAAOSwsXFZMakv&vxp=mtr

http://www.rockauto.com/en/parts/anchor,2254,motor+mount,5552

https://www.amazon.com/Westar-EM2254-Engine-Mount/dp/B000C995EQ

http://www.rockauto.com/en/parts/westar,EM2254,motor+mount,5552

"...(not sure if flywheel and clutch is the same as my sbc stuff I already have?..."

Will need a Pontiac flywheel. But, your clutch will probably work, especially if you buy one of the aftermarket flywheels that has more than one pressure plate bolt pattern. Will also need the correct size pilot bearing, to go in the end of the crank.

http://www.ebay.com/itm/PRW-Industries-1645570-Flywheel-/322481785615?_trksid=p2385738.m2548.l4275

http://butlerperformance.com/i-24452879-butler-pontiac-pilot-bearing-bop-ppb-126-bca-7109.html

"...Need new Hei distributor..."

Some consider the DUI brand HEI the best. But they are $305 @ Summit. There are cheaper units, on down to $50 Chinese models, which most don't recommend. Some like a Pertronix brand.

https://www.summitracing.com/parts/dui-51720bl/overview/make/pontiac

https://www.summitracing.com/parts/pnx-d1202/overview/make/pontiac

"...Exhaust modification..."

I always used Hedman #35270 headers. They also come in a #35276 coated version.

If you don't like headers, there are long branch exhaust manifolds, for D-port heads.

http://www.ramairrestoration.com/lb-1-long-branch-d-port-factory-headers.html

"...New fan shroud?..."

Repros are sold. Some say that most are not very good quality.

http://www.ebay.com/itm/NOS-PONTIAC-FIREBIRD-FAN-SHROUD-1967-1968-1969-8-CYLINDER-CARS-GEN-GM-/263104902613?hash=item3d424635d5:g:y6IAAOSwux5YNuSQ&vxp=mtr

https://www.oerparts.com/product/9788883b.html

http://www.jegs.com/i/OER/691/9788883/10002/-1


Would also recommend a Cold Case radiator, with 2 rows of 1.25" wide tubes. They're about $300 + shipping, but should cool a Pontiac engine.

http://www.firebirdcentral.com/1967_1969_Firebird_Aluminum_Radiator_Automatic_p/rad-404.htm