Without the model base model number & s/n number it is difficult to tell what engine it had. But here are some facts - I worked for AC for 14 year until 1982 & was the Product Mgr for the engine lifts.
1. The truck could also have an Allis Chalmers G153 engine in it or the Mitsubishi 4G153 or 154.
2. Under the Allis-Chalmers (Buda) name, trucks were made from 1953 until 1983/4. The manufacturing tools & design were sold to a company in Columbus Ohio & sold trucks under the banner ACMH - that company "died the death of a rag doll" and then Kalmar took over & marketed products under the brand Kalmar AC. Then Kalmar AC went out of the manufacturing business and had an OEM agreement with Komatsu to sell trucks (with red paint & different decals). Then Komatsu bought out Kalmar AC, later the name was changed to TUSK (same as Komatsu but with red paint different decals). About 2 years ago the TUSK name disappeared and Komatsu reorganized - US headquarters now in Illinois, Parts out of Tennessee, assembly in South Carolina.
Old Allis Chalmers parts "might" be available from Komatsu but those parts are some place near Kansas City, Mo (in an old mine shaft, I'm told).
3. With this history, in a nut shell, parts will be really hard to get in my opinion.
4. Don't get romanced by "low" hour meter reading - older hour meters (non digital) are a "fast moving" service part items & can be & will be changed faster than one changes underwear.
5. My opinion is keep your hands in your pockets off your wallet an/or check book & politely walk away & go shopping for a different dress. You won't find a good one for $1000. Remember that with todays scrap metal prices - you can get about $500 for a completely dead forklift.
6. If this unit was made by Allis-Chalmers the s/n number will be stamped in the frame.