A preliminary assessment of proof testing 13 prototypical liquid-metal fast breeder reactor (LMFBR) carbide fuel assemblies in fast test reactor (FTR) driver positions leads to the conclusion that the testing plan is practical and should produce a large amount of data at operating conditions very similar to those that would be found in large commercial carbide-fueled LMFBR s. Three subassembly configurations were designed, each capable of being directly substituted into FTR driver positions and made compatible with the FTR geometry, fuel handling, power, temperature, subassembly flow rates, and pin-bundle pressure drop. Two sodium-bonded designs, one with 91 fuel pins with a 0.370-in. o.d. and the other with 127 fuel pins with a 0.315-in. o.d. per subassembly were established. Calculated peak linear power and peak discharge burnup slightly exceed present commercial design objectives of 30 kW/ft and 73 MWd/kg. Individual assembly power history, flux, and enrichments are represented quite well in the FTR for commercial outer-zone fuel assemblies. Inner-zone operating conditions, however, are not simulated as closely. Impact effects of the proof-test assemblies on FTR operation are judged to be manageable.