Technical help needed decoding a chevy BB

trying to help out a buddy and go though a BB Chevy he had laying around uncovered for 25 years. it had been rebuilt then left to 'yes" a rusted but rebuild able mess. of what had been a badly done rebuild.
the casting number 3855961 with passenger tells me it is a 396/427 2 or 4 bolt used from 1965 to 1967 . this one is a 2 bolt ,the bore size is for a 030 over bore 396, front of the block under the timing cover and just under the left rear block deck has high performace cast in, the oil filter was a cartridge type, date code is a cast C1 with a 7 stamped in a small machined are by the c1. making me think march 1 1967,

what I can't find information on ,is the stamped date code, T1203IGR. I know the T means Tonawanda, New York Dec 3rd, normally the IG means a 325 hp 396 with a power glide, no where can I find a IGR engine performance code,

any one ever run across this one? for me I'm stumped as no where can I find what 396 a IGR is really made for. was it a special race code or a replacement IG
any help will be much thanked

 

Found a site that says IGR is 396-325 w/Rochester. IGH would be 396-325 w/Holley. Sounds reasonable.

 

20 seconds to do a quick search online:

" IGR 1966 396 325 PG B, Rochester "

I've only had 3 old 396s over the decades, and all were marked Hi Perf. I read years ago that it means nothing.

Someone will chime in on what's what with BBC

 

Only 5 seconds to search it at this end.
People never heard of Google?

that # is for a '65 -'66 396/325 or 360 hp chevelle or a passenger 396/325hp block

 

Way to help the guy out. Why bust his balls? Wow!

 

IG is a 67 full size car 396 325 hp with Powerglide. The R means it's a replacement engine.

at least that's how I understand it to work. I have a similar motor, IVR.

 

"I've only had 3 old 396s over the decades, and all were marked Hi Perf. I read years ago that it means nothing."

Almost all 2-piece rear seal BBC blocks 366-454 have Hi-Perf cast on them. Usually Hi-Perf Pass,(auto) Trk, (med duty truck)or Mar. (marine)

 

Really? specifically found "US", and that was the Q?
maybe ball busting is in order Let's hold hands and sing a song now...... Damn people, maybe that's a Q for ASK.COM!

 

Well at least his question gave you a chance to prove your superior knowledge to him and us. Sing away!

 

thanks guys. even the nut busters,
my starting points was my old Motors and Chilton's books first then turned to google and ask to start . as besides being a retired ASE master tech who had 45 back breaking years in dealership's like Malcolm Konner Chevy in new jersey in the 60's and auto machine shops building race motors , I'm also a Microsoft certified mscse or no dummy to computers .

the reason I asked in here as many of the old time gear heads and like me are now retired dealer techs, who have more in their heads then any computer can dig up. the block casting number was only 1965 or 66, 396 2 or 4 bolt main or possibly a 66 427, made for a passenger car, where it was assembled, the day, the IG code was used for 65 though 68 325 hp 396's with Q jets , that R stamped in with true matching design became a stumper.

a very big thank you to the man who came up with the Q jet answer, with your help I now know this one is a 1966 power glide Q jet 396 for a big body or a corvette

while the R for replacement makes some sense, some where in that time frame of late 60's early 70's GM started using the CE code for replacement motors. with many references to CE meaning Chevy engine, Crate engine, anything meaning replacement or over the counter sale