Here is some information you might need when looking for a LT1:
The 70-72 LT-1s did indeed use the HD u-joint caps normally reserved only for big blocks. The LT-1s also used a copper radiator and no expansion tank, so the presence of a tank (or holes on the psgr side fender) would mean a base engine no A/C car. The carb was actually a 780cfm vacuum secondary dual feed Holley and a single metal fuel running from the tank to the near the pump should be present. The 70-71 LT-1 also used Transistor pointelss ignition, so look for the amplifier box (or holes where the box was) on the left front side of the radiator (easiest seen by opening the hood and looking from the front of the car through the opening in the hood). Also, there was no Power Steering availalble on the 1970 LT-1 until about May of 70, so an early build car with PS would be suspect since the early 70 LT-1s used a larger 6 quart oil pan that would absolutely not fit with PS (the later cars went back to the normal 5 quart pan). The exhaust pipes on the LT-1 was also 2 1/2 inches whereas all other 70-72 small blocks used 2 inch (same manifolds used on all engines however). The tach redline for is 6500, the L-46 was 6000 and the base is 5300.
Now on the tranny, the LT-1 was just like any other small block Corvette. The car came standard with the M-20 Wide Ratio 4-speed, and the standard rear axle ratio was 3.55 to 1. Unless the buyer checked the M-21 Close Ratio box or another optional ratio with the M-20, the car was delivered with the M-20 and 3.55. Keeping the M-20, you could also order the Performance 3.70 ratio, or the Economy 3.36 ratio. The M-21 Close Ratio 4-speed was availalbe at no extra cost, and this combination gave you the 3.70 axle as standard, along with the Performance 4.11 or Economy 3.55 as options. The majority of LT-1s do indeed have the M-21 with the 3.70 or 4.11s, although many were built with the M-20. In 1972, when A/C was made availalbe in the middle of the year, you were not allowed to order the M-21 on the LT-1 in combination with the A/C, but had to keep the standard M-20 along with the 3.55 axle, and although the 3.36 axle could be had, the 3.70 could not be ordered with A/C. The M-22 tranny was technically an LT-1 option only in 1971 although some debate rages on this. In 1970, it is generally accepted that the M-22 tranny was included and only availalbe as part of RPO ZR-1 and could not be ordered as a seperate option on a standard LT-1. Again, you will hear differing opinions on M-22 usage, but with Chevrolet records showing 25 ZR-1s and 25 M-22s for 70 makes it pretty clear that all 25 M-22s went into the ZR-1s. In 71, it is the LS-6 engine that makes the picture a little foggy. For only the second time (the other year was 66), the M-22 tranny was on the books as a seperate option. Some guys say that it was only availalbe on the LS-6, but some say it could also be had on a standard LT-1. Since the M-22 equipped cars, used a special 12 3/4 inch lightweight flywheel and unique clutch, this would have required many different parts to use the M-22 on the LT-1, this would have complicated the build issue and seems like something Chevy would not have wanted to do, but it is possible. For 72, the only Corvettes to use the M-22 was the ZR-1.
The suspensions on all LT-1s was exactly like the base engine cars, except for 71 where the stiff F-41 setup could be ordered as a stand alone option without having to buy the complete heavy duty car (ZR-1).
There are several "one year only" parts on a 1970 that can get expensive to replace if they are not there. The front grills are specific for that year- they had studs and not screws for two of the acttachment points. The more common grills for 1971-1972 have 4 screws. 1970 also has different windshield washer pump with 5 ports. If it is a 350/350hp car, the original carb Quadrajet 7040207 can easily run $750. I would also check the numbers and see if they match (engine/transmission).
Check the fuel line. The LT-1 had only one fuel line coming from the tank and no return line running along with it. I have a 70 350/300 and it has the return line.
If it has the original alternator, the pully should be machined from a solid stock as opposed to a stamped unit. Also being a 70, there should be indications that it does not, nor ever had air conditioning.
Check the red line on the tach-6500 for 350 and 370 hp
The carb is very rare if it's a 4555-make sure it has the three digit date code, not 4 digits(remanufac'd)
The fuel line splits before it goes to the front and rear bowls joined by a brass "T". (70 and 71 LT-1s)
The fuel pump is a 40709 (70 and 71 LT-1s)base is a 40769
Check the coil, should be a 272, very rare
Distrib.-1111491 (LT-1 only)check band at the base for part# and date.
Vacuum advance part #- 201 16 (70 LT-1 only)
Exhaust manifolds should have plugged A.I.R. holes if the system is gone.
Alternator should be a 1100884, 61 amp (all air cond. cars or LT-1 70's)
8" diameter harmonic dampner (LT-1s and BB)plus they are thicker
White emission label with "CL" or "CT" code
TI harness is wraped with DULL BLK CLOTH tape, not the gloss black
tape on the main harness.
