Soviet SP gun SU76i
This is the LEVA Productions SU-76i resin conversion, kit #72-C-01. It is technically 1/76 scale for the Matchbox Pz III kit and is LEVA's only 1/76 scale conversion. I mated it to the ESCI Pz III kit and find it worked well. The conversion looks accurate in features. The conversion consists of three major resin parts (Body, gun with mantlet, and flat shield for the mantlet) and several small resin parts. The rest of the parts come from the model kit you chose. ESCI T-34 spare fuel tanks were used.
Though the ESCI roadwheels and sprockets were used, I opted for Revell's much better Pz III tracks. When attaching the tracks onto the sprocket I discovered that Revells tracks are too narrow for the sprocket teeth and do not look right. When assembling the ESCI sprocket wheels in this case I should have made the sprocket about 2-mm narrower.
No instructions were supplied with the LEVA kit. Photos of about six different SU-76i assault guns show many small variations in features. Markings are typical of captured tanks but match no particular vehicle. The finish is done if Model Master and Tamiya acrylics.
I have read that several hundred of these vehicles were produced and fielded in 1943 from captured German Pz III tanks and Sturngeschutz III's, particularly from those captured at Stalingrad. There were even several rebuilt on Pz IV chassis. I understand that the Germans fielded a dozen or so that they captured back from the Soviets.